How do I read convert an InputStream into a String in Java

Question

If you have a java io InputStream object  how should you process that object and produce a String     Suppose I have an InputStream that contains text data  and I want to convert it to a String  so for example I can write that to a log file   What is the easiest way to take the InputStream and convert it to a String   public String convertStreamToString InputStream is

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Apache Commons allows   String myString   IOUtils toString myInputStream   UTF-8      Of course  you could choose other character encodings besides UTF-8   Also see   documentation

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Well  you can program it for yourself    It s not complicated     String Inputstream2String  InputStream is  throws IOException               final int PKG SIZE   1024          byte   data   new byte  PKG SIZE           StringBuilder buffer   new StringBuilder PKG SIZE   10           int size           size   is read data  0  data length           while  size  gt  0                        String str   new String data  0  size               buffer append str               size   is read data  0  data length                     return buffer toString

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I d use some Java 8 tricks   public static String streamToString final InputStream inputStream  throws Exception          buffering optional     try               final BufferedReader br              new BufferedReader new InputStreamReader inputStream                      parallel optional         return br lines   parallel   collect Collectors joining   n           catch  final IOException e            throw new RuntimeException e              whatever            Essentially the same as some other answers except more succinct

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I suggest the StringWriter class for that problem   StringWriter wt  new StringWriter    IOUtils copy inputStream  wt  encoding   String st  wt toString

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I suggest the StringWriter class for that problem   StringWriter wt  new StringWriter    IOUtils copy inputStream  wt  encoding   String st  wt toString

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You can use Cactoos   String text   new TextOf inputStream  asString      UTF-8 encoding is the default one  If you need another one   String text   new TextOf inputStream   UTF-16   asString

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If you were feeling adventurous  you could mix Scala and Java and end up with this   scala io Source fromInputStream is  mkString       Mixing Java and Scala code and libraries has it s benefits   See full description here  Idiomatic way to convert an InputStream to a String in Scala

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This Code is for New Java Learners         private String textDataFromFile   public String getFromFile InputStream myInputStream  throws FileNotFoundException  IOException          BufferedReader bufferReader   new BufferedReader  new InputStreamReader myInputStream            StringBuilder stringBuilder   new StringBuilder       String eachStringLine       while  eachStringLine bufferReader readLine       null                     stringBuilder append eachStringLine  append   n              textDataFromFile   stringBuilder toString          return textDataFromFile

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Apache Commons allows   String myString   IOUtils toString myInputStream   UTF-8      Of course  you could choose other character encodings besides UTF-8   Also see   documentation

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InputStream IS new URL  http   www petrol si api gas prices json   openStream          ByteArrayOutputStream BAOS new ByteArrayOutputStream      IOUtils copy IS  BAOS     String d  new String BAOS toByteArray    UTF-8                System out println d

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This solution to this question is not the simplest  but since NIO streams and channels have not been mentioned  here goes a version which uses NIO channels and a ByteBuffer to convert a stream into a string   public static String streamToStringChannel InputStream in  String encoding  int bufSize  throws IOException       ReadableByteChannel channel   Channels newChannel in       ByteBuffer byteBuffer   ByteBuffer allocate bufSize       ByteArrayOutputStream bout   new ByteArrayOutputStream        WritableByteChannel outChannel   Channels newChannel bout       while  channel read byteBuffer   gt  0    byteBuffer position    gt  0            byteBuffer flip       make buffer ready for write         outChannel write byteBuffer           byteBuffer compact      make buffer ready for reading           channel close        outChannel close        return bout toString encoding       Here is an example how to use it   try  InputStream in   new FileInputStream   tmp large file xml          String x   streamToStringChannel in   UTF-8   1       System out println x       The performance of this method should be good for large files

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I ran some timing tests because time matters  always   I attempted to get the response into a String 3 different ways   shown below  I left out try catch blocks for the sake readability   To give context  this is the preceding code for all 3 approaches      String response     String url    www blah com path key value      GetMethod method   new GetMethod url      int status   client executeMethod method     1    response   method getResponseBodyAsString      2   InputStream resp   method getResponseBodyAsStream    InputStreamReader is new InputStreamReader resp   BufferedReader br new BufferedReader is   String read   null  StringBuffer sb   new StringBuffer    while  read   br readLine       null        sb append read     response   sb toString      3   InputStream iStream    method getResponseBodyAsStream    StringWriter writer   new StringWriter    IOUtils copy iStream  writer   UTF-8    response   writer toString      So  after running 500 tests on each approach with the same request response data  here are the numbers  Once again  these are my findings and your findings may not be exactly the same  but I wrote this to give some indication to others of the efficiency differences of these approaches   Ranks  Approach  1 Approach  3 - 2 6  slower than  1 Approach  2 - 4 3  slower than  1  Any of these approaches is an appropriate solution for grabbing a response and creating a String from it

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InputStream is   Context openFileInput someFileName      whatever format you have  ByteArrayOutputStream bos   new ByteArrayOutputStream     byte   b   new byte 8192   for  int bytesRead   bytesRead   is read b      -1         bos write b  0  bytesRead      String output   bos toString someEncoding

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This Code is for New Java Learners         private String textDataFromFile   public String getFromFile InputStream myInputStream  throws FileNotFoundException  IOException          BufferedReader bufferReader   new BufferedReader  new InputStreamReader myInputStream            StringBuilder stringBuilder   new StringBuilder       String eachStringLine       while  eachStringLine bufferReader readLine       null                     stringBuilder append eachStringLine  append   n              textDataFromFile   stringBuilder toString          return textDataFromFile

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A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter    something like  StringWriter writer   new StringWriter    IOUtils copy inputStream  writer  encoding   String theString   writer toString      or even     NB  does not close inputStream  you ll have to use try-with-resources for that String theString   IOUtils toString inputStream  encoding      Alternatively  you could use ByteArrayOutputStream if you don t want to mix your Streams and Writers

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Use   import java io BufferedInputStream  import java io ByteArrayOutputStream  import java io InputStream  import java io IOException   public static String readInputStreamAsString InputStream in      throws IOException        BufferedInputStream bis   new BufferedInputStream in       ByteArrayOutputStream buf   new ByteArrayOutputStream        int result   bis read        while result    -1          byte b    byte result        buf write b         result   bis read              return buf toString

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InputStreamReader i   new InputStreamReader s   BufferedReader str   new BufferedReader i   String msg   str readLine    System out println msg     Here s is your InputStream object which will get convert into String

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InputStream  inputStream   null  BufferedReader bufferedReader   null  try       BufferedReader bufferedReader   new BufferedReader new InputStreamReader inputStream        String stringBuilder   new StringBuilder        String content      while  content   bufferedReader readLine       null           stringBuilder append content             System out println  content of file      stringBuilder toString       catch  IOException e                e printStackTrace             finally                         if bufferedReader    null                   try                      bufferedReader close                     catch IoException ex                      ex printStackTrace

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I d use some Java 8 tricks   public static String streamToString final InputStream inputStream  throws Exception          buffering optional     try               final BufferedReader br              new BufferedReader new InputStreamReader inputStream                      parallel optional         return br lines   parallel   collect Collectors joining   n           catch  final IOException e            throw new RuntimeException e              whatever            Essentially the same as some other answers except more succinct

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Here s my Java 8 based solution  which uses the new Stream API to collect all lines from an InputStream   public static String toString InputStream inputStream        BufferedReader reader   new BufferedReader          new InputStreamReader inputStream        return reader lines   collect Collectors joining          System getProperty  line separator

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Quick and easy   String result    String new ObjectInputStream  inputStream   readObject

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In terms of reduce  and concat it can be expressed in Java 8 as   String fromFile   new BufferedReader new    InputStreamReader inputStream   lines   reduce String  concat  get

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In Groovy  inputStream getText

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I have created this code  and it works  There are no required external plug-ins   There is a converter String to Stream and Stream to String   import java io ByteArrayInputStream  import java io InputStream   public class STRINGTOSTREAM        public static void main String   args                String text    Hello Bhola    nMy Name Is Kishan             InputStream strm   new ByteArrayInputStream text getBytes           Convert String to Stream          String data   streamTostring strm            System out println data              static String streamTostring InputStream stream                String data                try                       StringBuilder stringbuld   new StringBuilder                int i              while   i stream read     -1                                stringbuld append  char i                             data   stringbuld toString                      catch Exception e                        data    No data Streamed                      return data

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This one is nice because    It safely handles the Charset  You control the read buffer size  You can provision the length of the builder and it doesn t have to be an exact value  Is free from library dependencies  Is for Java 7 or higher    How to do it   public static String convertStreamToString InputStream is  throws IOException      StringBuilder sb   new StringBuilder 2048      Define a size if you have an idea of it     char   read   new char 128      Your buffer size     try  InputStreamReader ir   new InputStreamReader is  StandardCharsets UTF 8          for  int i  -1     i   ir read read    sb append read  0  i            return sb toString        For JDK 9  public static String inputStreamString InputStream inputStream  throws IOException       try  inputStream            return new String inputStream readAllBytes    StandardCharsets UTF 8

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With Okio   String result   Okio buffer Okio source inputStream   readUtf8

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JDK 7 8 answer that closes the stream and still throws an IOException   StringBuilder build   new StringBuilder    byte   buf   new byte 1024   int length  try  InputStream is   getInputStream        while   length   is read buf      -1        build append new String buf  0  length

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A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter    something like  StringWriter writer   new StringWriter    IOUtils copy inputStream  writer  encoding   String theString   writer toString      or even     NB  does not close inputStream  you ll have to use try-with-resources for that String theString   IOUtils toString inputStream  encoding      Alternatively  you could use ByteArrayOutputStream if you don t want to mix your Streams and Writers

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This is an answer adapted from org apache commons io IOUtils source code  for those who want to have the apache implementation but do not want the whole library   private static final int BUFFER SIZE   4   1024   public static String inputStreamToString InputStream inputStream  String charsetName          throws IOException       StringBuilder builder   new StringBuilder        InputStreamReader reader   new InputStreamReader inputStream  charsetName       char   buffer   new char BUFFER SIZE       int length      while   length   reader read buffer      -1            builder append buffer  0  length             return builder toString

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This one is nice because    It safely handles the Charset  You control the read buffer size  You can provision the length of the builder and it doesn t have to be an exact value  Is free from library dependencies  Is for Java 7 or higher    How to do it   public static String convertStreamToString InputStream is  throws IOException      StringBuilder sb   new StringBuilder 2048      Define a size if you have an idea of it     char   read   new char 128      Your buffer size     try  InputStreamReader ir   new InputStreamReader is  StandardCharsets UTF 8          for  int i  -1     i   ir read read    sb append read  0  i            return sb toString        For JDK 9  public static String inputStreamString InputStream inputStream  throws IOException       try  inputStream            return new String inputStream readAllBytes    StandardCharsets UTF 8

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Taking into account file one should first get a java io Reader instance  This can then be read and added to a StringBuilder  we don t need StringBuffer if we are not accessing it in multiple threads  and StringBuilder is faster   The trick here is that we work in blocks  and as such don t need other buffering streams  The block size is parameterized for run-time performance optimization   public static String slurp final InputStream is  final int bufferSize        final char   buffer   new char bufferSize       final StringBuilder out   new StringBuilder        try  Reader in   new InputStreamReader is   UTF-8              for                    int rsz   in read buffer  0  buffer length               if  rsz  lt  0                  break              out append buffer  0  rsz                       catch  UnsupportedEncodingException ex                                catch  IOException ex                                return out toString

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Here s how to do it using just the JDK using byte array buffers  This is actually how the commons-io IOUtils copy   methods all work  You can replace byte   with char   if you re copying from a Reader instead of an InputStream   import java io ByteArrayOutputStream  import java io InputStream        InputStream is        ByteArrayOutputStream baos   new ByteArrayOutputStream 8192   byte   buffer   new byte 8192   int count   0  try     while   count   is read buffer      -1        baos write buffer  0  count         finally     try       is close          catch  Exception ignore           String charset    UTF-8   String inputStreamAsString   baos toString charset

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I have written a class that does just that  so I figured I d share it with everyone  Sometimes you don t want to add Apache Commons just for one thing  and want something dumber than Scanner that doesn t examine the content   Usage is as follows     Read from InputStream String data   new ReaderSink inputStream  Charset forName  UTF-8    drain        Read from File data   new ReaderSink file  Charset forName  UTF-8    drain        Drain input stream to console new ReaderSink inputStream  Charset forName  UTF-8    drainTo System out     Here is the code for ReaderSink   import java io    import java nio charset Charset          A simple sink class that drains a   link Reader  to a   link String  or    to a   link Writer          author Ben Barkay     version 2 20 2014     public class ReaderSink                  The default buffer size to use if no buffer size was specified              public static final int DEFAULT BUFFER SIZE   1024                  The   link Reader  that will be drained              private final Reader in                  Constructs a new   code ReaderSink  for the specified file and charset          param file      The file to read from          param charset   The charset to use          throws FileNotFoundException    If the file was not found on the filesystem              public ReaderSink File file  Charset charset  throws FileNotFoundException           this new FileInputStream file   charset                         Constructs a new   code ReaderSink  for the specified   link InputStream           param in        The   link InputStream  to drain          param charset   The charset to use              public ReaderSink InputStream in  Charset charset            this new InputStreamReader in  charset                          Constructs a new   code ReaderSink  for the specified   link Reader           param in    The reader to drain              public ReaderSink Reader in            this in   in                        Drains the data from the underlying   link Reader   returning a   link String  containing        all of the read information  This method will use   link  DEFAULT BUFFER SIZE  for        its buffer size          return  A   link String  containing all of the information that was read              public String drain   throws IOException           return drain DEFAULT BUFFER SIZE                         Drains the data from the underlying   link Reader   returning a   link String  containing        all of the read information          param bufferSize    The size of the buffer to use when reading          return  A   link String  containing all of the information that was read              public String drain int bufferSize  throws IOException           StringWriter stringWriter   new StringWriter            drainTo stringWriter  bufferSize           return stringWriter toString                          Drains the data from the underlying   link Reader   writing it to the        specified   link Writer   This method will use   link  DEFAULT BUFFER SIZE  for        its buffer size          param out   The   link Writer  to write to              public void drainTo Writer out  throws IOException           drainTo out  DEFAULT BUFFER SIZE                         Drains the data from the underlying   link Reader   writing it to the        specified   link Writer           param out           The   link Writer  to write to          param bufferSize    The size of the buffer to use when reader              public void drainTo Writer out  int bufferSize  throws IOException           char   buffer   new char bufferSize           int read          while   read   in read buffer    gt  -1                out write buffer  0  read

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Also you can get InputStream from a specified resource path   public static InputStream getResourceAsStream String path        InputStream myiInputStream   ClassName class getResourceAsStream path       if  null    myiInputStream                mylogger info  Can t find path      path              return myiInputStream      To get InputStream from a specific path   public static URL getResource String path        URL myURL   ClassName class getResource path       if  null    myURL                mylogger info  Can t find resource path      path             return myURL

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If you can t use Commons IO  FileUtils IOUtils CopyUtils   here s an example using a BufferedReader to read the file line by line   public class StringFromFile       public static void main String   args    throws UnsupportedEncodingException             InputStream is   StringFromFile class getResourceAsStream  file txt            BufferedReader br   new BufferedReader new InputStreamReader is     UTF-8               final int CHARS PER PAGE   5000    counting spaces         StringBuilder builder   new StringBuilder CHARS PER PAGE           try               for String line br readLine    line  null  line br readLine                      builder append line                   builder append   n                                     catch  IOException ignore               String text   builder toString            System out println text             Or if you want raw speed I d propose a variation on what Paul de Vrieze suggested  which avoids using a StringWriter  which uses a StringBuffer internally    public class StringFromFileFast       public static void main String   args    throws UnsupportedEncodingException             InputStream is   StringFromFileFast class getResourceAsStream  file txt            InputStreamReader input   new InputStreamReader is     UTF-8              final int CHARS PER PAGE   5000    counting spaces         final char   buffer   new char CHARS PER PAGE           StringBuilder output   new StringBuilder CHARS PER PAGE           try               for int read   input read buffer  0  buffer length                       read    -1                      read   input read buffer  0  buffer length                     output append buffer  0  read                           catch  IOException ignore               String text   output toString            System out println text

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Use the java io InputStream transferTo OutputStream  supported in Java 9 and the ByteArrayOutputStream toString String  which takes the charset name   public static String gobble InputStream in  String charsetName  throws IOException       ByteArrayOutputStream bos   new ByteArrayOutputStream        in transferTo bos       return bos toString charsetName

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You can use Apache Commons   In the IOUtils you can find the toString method with three helpful implementations   public static String toString InputStream input  throws IOException           return toString input  Charset defaultCharset        public static String toString InputStream input  throws IOException           return toString input  Charset defaultCharset        public static String toString InputStream input  String encoding              throws IOException           return toString input  Charsets toCharset encoding

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Method to convert inputStream to String  public static String getStringFromInputStream InputStream inputStream         BufferedReader bufferedReader   null      StringBuilder stringBuilder   new StringBuilder        String line       try           bufferedReader   new BufferedReader new InputStreamReader                  inputStream            while   line   bufferedReader readLine       null                stringBuilder append line                   catch  IOException e            logger error e getMessage           finally           if  bufferedReader    null                try                   bufferedReader close                  catch  IOException e                    logger error e getMessage                                       return stringBuilder toString

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Note  This probably isn t a good idea  This method uses recursion and thus will hit a StackOverflowError very quickly   public String read  InputStream is        byte next   is read        return next    -1        next   read is      Recursive part  reads next byte recursively     Please don t downvote this just because it s a bad choice to use  this was mostly creative

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Here s my Java 8 based solution  which uses the new Stream API to collect all lines from an InputStream   public static String toString InputStream inputStream        BufferedReader reader   new BufferedReader          new InputStreamReader inputStream        return reader lines   collect Collectors joining          System getProperty  line separator

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I have created this code  and it works  There are no required external plug-ins   There is a converter String to Stream and Stream to String   import java io ByteArrayInputStream  import java io InputStream   public class STRINGTOSTREAM        public static void main String   args                String text    Hello Bhola    nMy Name Is Kishan             InputStream strm   new ByteArrayInputStream text getBytes           Convert String to Stream          String data   streamTostring strm            System out println data              static String streamTostring InputStream stream                String data                try                       StringBuilder stringbuld   new StringBuilder                int i              while   i stream read     -1                                stringbuld append  char i                             data   stringbuld toString                      catch Exception e                        data    No data Streamed                      return data

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Here is the complete method for converting InputStream into String without using any third party library  Use StringBuilder for single threaded environment otherwise use StringBuffer     public static String getString  InputStream is  throws IOException       int ch      StringBuilder sb   new StringBuilder        while  ch   is read       -1          sb append  char ch       return sb toString

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You can use Cactoos   String text   new TextOf inputStream  asString      UTF-8 encoding is the default one  If you need another one   String text   new TextOf inputStream   UTF-16   asString

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String inputStreamToString InputStream inputStream  Charset charset  throws IOException       try               final StringWriter writer   new StringWriter                final InputStreamReader reader   new InputStreamReader inputStream  charset                      reader transferTo writer           return writer toString               pure Java standard library solution - no libs since Java 10 - Reader transferTo java io Writer  loopless solution no new line character handling

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The following doesn t address the original question  but rather some of the responses   Several responses suggest loops of the form  String line   null  while  line   reader readLine       null                 or  for String line   reader readLine    line    null  line   reader readLine                     The first form pollutes the namespace of the enclosing scope by declaring a variable  read  in the enclosing scope that will not be used for anything outside the for loop  The second form duplicates the readline   call   Here is a much cleaner way of writing this sort of loop in Java  It turns out that the first clause in a for-loop doesn t require an actual initializer value  This keeps the scope of the variable  line  to within the body of the for loop  Much more elegant  I haven t seen anybody using this form anywhere  I randomly discovered it one day years ago   but I use it all the time   for  String line   line   reader readLine       null

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Here s more-or-less sampath s answer  cleaned up a bit and represented as a function   String streamToString InputStream in  throws IOException     StringBuilder out   new StringBuilder      BufferedReader br   new BufferedReader new InputStreamReader in      for String line   br readLine    line    null  line   br readLine         out append line     br close      return out toString

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ISO-8859-1  Here is a very performant way to do this if you know your input stream s encoding is ISO-8859-1 or ASCII  It  1  avoids the unnecessary synchronization present in StringWriter s internal StringBuffer   2  avoids the overhead of InputStreamReader  and  3  minimizes the number of times StringBuilder s internal char array must be copied   public static String iso 8859 1 InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  chars append  char  buffer i   amp  0xFF                        return chars toString        UTF-8  The same general strategy may be used for a stream encoded with UTF-8    public static String utf8 InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      int state   0      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  if   state   nextStateUtf8 state  buffer i     gt   0                    chars appendCodePoint state                 else if  state    -1      error                 state   0                  chars append   uFFFD      replacement char                                   return chars toString        where the nextStateUtf8   function is defined as follows          Returns the next UTF-8 state given the next byte of input and the current state     If the input byte is the last byte in a valid UTF-8 byte sequence     the returned state will be the corresponding unicode character  in the range of 0 through 0x10FFFF      Otherwise  a negative integer is returned  A state of -1 is returned whenever an    invalid UTF-8 byte sequence is detected      static int nextStateUtf8 int currentState  byte nextByte        switch  currentState  amp  0xF0000000            case 0              if   nextByte  amp  0x80     0      0 trailing bytes  ASCII                  return nextByte                else if   nextByte  amp  0xE0     0xC0      1 trailing byte                 if  nextByte     byte  0xC0    nextByte     byte  0xC1      0xCO  amp  0xC1 are overlong                     return -1                    else                       return nextByte  amp  0xC000001F                                  else if   nextByte  amp  0xF0     0xE0      2 trailing bytes                 if  nextByte     byte  0xE0      possibly overlong                     return nextByte  amp  0xA000000F                    else if  nextByte     byte  0xED      possibly surrogate                     return nextByte  amp  0xB000000F                    else                       return nextByte  amp  0x9000000F                                  else if   nextByte  amp  0xFC     0xF0      3 trailing bytes                 if  nextByte     byte  0xF0      possibly overlong                     return nextByte  amp  0x80000007                    else                       return nextByte  amp  0xE0000007                                  else if  nextByte     byte  0xF4      3 trailing bytes  possibly undefined                 return nextByte  amp  0xD0000007                else                   return -1                        case 0xE0000000    3rd-to-last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0x80000000    3rd-to-last continuation byte  check overlong             return  nextByte  amp  0xE0     0xA0     nextByte  amp  0xF0     0x90   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0xD0000000    3rd-to-last continuation byte  check undefined             return  nextByte  amp  0xF0     0x80   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0x90000000    2nd-to-last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xA0000000    2nd-to-last continuation byte  check overlong             return  nextByte  amp  0xE0     0xA0   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xB0000000    2nd-to-last continuation byte  check surrogate             return  nextByte  amp  0xE0     0x80   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xC0000000    last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0x3F   -1          default              return -1            Auto-Detect Encoding  If your input stream was encoded using either ASCII or ISO-8859-1 or UTF-8  but you re not sure which  we can use a similar method to the last  but with an additional encoding-detection component to auto-detect the encoding before returning the string   public static String autoDetect InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      int state   0      boolean ascii   true      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  if   state   nextStateUtf8 state  buffer i     gt  0x7F                  ascii   false              chars append  char  buffer i   amp  0xFF                         if  ascii    state  lt  0      probably not UTF-8         return chars toString                probably UTF-8     int pos   0      char   charBuf   new char 2       for  int i   0  len   chars length    i  lt  len  i              if   state   nextStateUtf8 state   byte chars charAt i     gt   0                boolean hi   Character toChars state  charBuf  0     2              chars setCharAt pos    charBuf 0                if  hi                    chars setCharAt pos    charBuf 1                                      return chars substring 0  pos       If your input stream has an encoding that is neither ISO-8859-1 nor ASCII nor UTF-8  then I defer to the other answers already present

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Use   InputStream in      Your InputStream     StringBuilder sb   new StringBuilder    BufferedReader br   new BufferedReader new InputStreamReader in    String read   while   read br readLine       null          System out println read       sb append read      br close    return sb toString

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Summarize other answers I found 11 main ways to do this  see below   And I wrote some performance tests  see results below   Ways to convert an InputStream to a String   Using IOUtils toString  Apache Utils   String result   IOUtils toString inputStream  StandardCharsets UTF 8     Using CharStreams  Guava   String result   CharStreams toString new InputStreamReader         inputStream  Charsets UTF 8      Using Scanner  JDK   Scanner s   new Scanner inputStream  useDelimiter  quot   A quot     String result   s hasNext     s next      quot  quot     Using Stream API  Java 8   Warning  This solution converts different line breaks  like  r n  to  n   String result   new BufferedReader new InputStreamReader inputStream       lines   collect Collectors joining  quot  n quot       Using parallel Stream API  Java 8   Warning  This solution converts different line breaks  like  r n  to  n   String result   new BufferedReader new InputStreamReader inputStream        lines   parallel   collect Collectors joining  quot  n quot       Using InputStreamReader and StringBuilder  JDK   int bufferSize   1024   char   buffer   new char bufferSize    StringBuilder out   new StringBuilder     Reader in   new InputStreamReader stream  StandardCharsets UTF 8    for  int numRead   numRead   in read buffer  0  buffer length    gt  0           out append buffer  0  numRead       return out toString      Using StringWriter and IOUtils copy  Apache Commons   StringWriter writer   new StringWriter     IOUtils copy inputStream  writer   quot UTF-8 quot     return writer toString      Using ByteArrayOutputStream and inputStream read  JDK   ByteArrayOutputStream result   new ByteArrayOutputStream     byte   buffer   new byte 1024    for  int length   length   inputStream read buffer      -1           result write buffer  0  length          StandardCharsets UTF 8 name    gt  JDK 7  return result toString  quot UTF-8 quot      Using BufferedReader  JDK   Warning  This solution converts different line breaks  like  n r  to line separator system property  for example  in Windows to  quot  r n quot     String newLine   System getProperty  quot line separator quot     BufferedReader reader   new BufferedReader           new InputStreamReader inputStream     StringBuilder result   new StringBuilder     for  String line   line   reader readLine       null           if  result length    gt  0             result append newLine               result append line       return result toString      Using BufferedInputStream and ByteArrayOutputStream  JDK  BufferedInputStream bis   new BufferedInputStream inputStream   ByteArrayOutputStream buf   new ByteArrayOutputStream    for  int result   bis read    result    -1  result   bis read          buf write  byte  result        StandardCharsets UTF 8 name    gt  JDK 7 return buf toString  quot UTF-8 quot      Using inputStream read   and StringBuilder  JDK   Warning  This solution has problems with Unicode  for example with Russian text  works correctly only with non-Unicode text  StringBuilder sb   new StringBuilder    for  int ch   ch   inputStream read       -1          sb append  char  ch     return sb toString       Warning   Solutions 4  5 and 9 convert different line breaks to one   Solution 11 can t work correctly with Unicode text   Performance tests Performance tests for small String  length   175   url in github  mode   Average Time  system   Linux  score 1 343 is the best                 Benchmark                         Mode  Cnt   Score   Error  Units  8  ByteArrayOutputStream and read  JDK         avgt   10   1 343    0 028  us op  6  InputStreamReader and StringBuilder  JDK    avgt   10   6 980    0 404  us op 10  BufferedInputStream  ByteArrayOutputStream  avgt   10   7 437    0 735  us op 11  InputStream read   and StringBuilder  JDK   avgt   10   8 977    0 328  us op  7  StringWriter and IOUtils copy  Apache       avgt   10  10 613    0 599  us op  1  IOUtils toString  Apache Utils              avgt   10  10 605    0 527  us op  3  Scanner  JDK                                avgt   10  12 083    0 293  us op  2  CharStreams  guava                          avgt   10  12 999    0 514  us op  4  Stream Api  Java 8                          avgt   10  15 811    0 605  us op  9  BufferedReader  JDK                         avgt   10  16 038    0 711  us op  5  parallel Stream Api  Java 8                 avgt   10  21 544    0 583  us op  Performance tests for big String  length   50100   url in github  mode   Average Time  system   Linux  score 200 715 is the best                  Benchmark                        Mode  Cnt   Score        Error  Units  8  ByteArrayOutputStream and read  JDK         avgt   10   200 715      18 103  us op  1  IOUtils toString  Apache Utils              avgt   10   300 019       8 751  us op  6  InputStreamReader and StringBuilder  JDK    avgt   10   347 616     130 348  us op  7  StringWriter and IOUtils copy  Apache       avgt   10   352 791     105 337  us op  2  CharStreams  guava                          avgt   10   420 137      59 877  us op  9  BufferedReader  JDK                         avgt   10   632 028      17 002  us op  5  parallel Stream Api  Java 8                 avgt   10   662 999      46 199  us op  4  Stream Api  Java 8                          avgt   10   701 269      82 296  us op 10  BufferedInputStream  ByteArrayOutputStream  avgt   10   740 837       5 613  us op  3  Scanner  JDK                                avgt   10   751 417      62 026  us op 11  InputStream read   and StringBuilder  JDK   avgt   10  2919 350    1101 942  us op  Graphs  performance tests depending on Input Stream length in Windows 7 system   Performance test  Average Time  depending on Input Stream length in Windows 7 system   length  182    546     1092    3276    9828    29484   58968   test8  0 38    0 938   1 868   4 448   13 412  36 459  72 708  test4  2 362   3 609   5 573   12 769  40 74   81 415  159 864  test5  3 881   5 075   6 904   14 123  50 258  129 937 166 162  test9  2 237   3 493   5 422   11 977  45 98   89 336  177 39  test6  1 261   2 12    4 38    10 698  31 821  86 106  186 636  test7  1 601   2 391   3 646   8 367   38 196  110 221 211 016  test1  1 529   2 381   3 527   8 411   40 551  105 16  212 573  test3  3 035   3 934   8 606   20 858  61 571  118 744 235 428  test2  3 136   6 238   10 508  33 48   43 532  118 044 239 481  test10 1 593   4 736   7 527   20 557  59 856  162 907 323 147  test11 3 913   11 506  23 26   68 644  207 591 600 444 1211 545

User · Answer

Summarize other answers I found 11 main ways to do this  see below   And I wrote some performance tests  see results below   Ways to convert an InputStream to a String   Using IOUtils toString  Apache Utils   String result   IOUtils toString inputStream  StandardCharsets UTF 8     Using CharStreams  Guava   String result   CharStreams toString new InputStreamReader         inputStream  Charsets UTF 8      Using Scanner  JDK   Scanner s   new Scanner inputStream  useDelimiter  quot   A quot     String result   s hasNext     s next      quot  quot     Using Stream API  Java 8   Warning  This solution converts different line breaks  like  r n  to  n   String result   new BufferedReader new InputStreamReader inputStream       lines   collect Collectors joining  quot  n quot       Using parallel Stream API  Java 8   Warning  This solution converts different line breaks  like  r n  to  n   String result   new BufferedReader new InputStreamReader inputStream        lines   parallel   collect Collectors joining  quot  n quot       Using InputStreamReader and StringBuilder  JDK   int bufferSize   1024   char   buffer   new char bufferSize    StringBuilder out   new StringBuilder     Reader in   new InputStreamReader stream  StandardCharsets UTF 8    for  int numRead   numRead   in read buffer  0  buffer length    gt  0           out append buffer  0  numRead       return out toString      Using StringWriter and IOUtils copy  Apache Commons   StringWriter writer   new StringWriter     IOUtils copy inputStream  writer   quot UTF-8 quot     return writer toString      Using ByteArrayOutputStream and inputStream read  JDK   ByteArrayOutputStream result   new ByteArrayOutputStream     byte   buffer   new byte 1024    for  int length   length   inputStream read buffer      -1           result write buffer  0  length          StandardCharsets UTF 8 name    gt  JDK 7  return result toString  quot UTF-8 quot      Using BufferedReader  JDK   Warning  This solution converts different line breaks  like  n r  to line separator system property  for example  in Windows to  quot  r n quot     String newLine   System getProperty  quot line separator quot     BufferedReader reader   new BufferedReader           new InputStreamReader inputStream     StringBuilder result   new StringBuilder     for  String line   line   reader readLine       null           if  result length    gt  0             result append newLine               result append line       return result toString      Using BufferedInputStream and ByteArrayOutputStream  JDK  BufferedInputStream bis   new BufferedInputStream inputStream   ByteArrayOutputStream buf   new ByteArrayOutputStream    for  int result   bis read    result    -1  result   bis read          buf write  byte  result        StandardCharsets UTF 8 name    gt  JDK 7 return buf toString  quot UTF-8 quot      Using inputStream read   and StringBuilder  JDK   Warning  This solution has problems with Unicode  for example with Russian text  works correctly only with non-Unicode text  StringBuilder sb   new StringBuilder    for  int ch   ch   inputStream read       -1          sb append  char  ch     return sb toString       Warning   Solutions 4  5 and 9 convert different line breaks to one   Solution 11 can t work correctly with Unicode text   Performance tests Performance tests for small String  length   175   url in github  mode   Average Time  system   Linux  score 1 343 is the best                 Benchmark                         Mode  Cnt   Score   Error  Units  8  ByteArrayOutputStream and read  JDK         avgt   10   1 343    0 028  us op  6  InputStreamReader and StringBuilder  JDK    avgt   10   6 980    0 404  us op 10  BufferedInputStream  ByteArrayOutputStream  avgt   10   7 437    0 735  us op 11  InputStream read   and StringBuilder  JDK   avgt   10   8 977    0 328  us op  7  StringWriter and IOUtils copy  Apache       avgt   10  10 613    0 599  us op  1  IOUtils toString  Apache Utils              avgt   10  10 605    0 527  us op  3  Scanner  JDK                                avgt   10  12 083    0 293  us op  2  CharStreams  guava                          avgt   10  12 999    0 514  us op  4  Stream Api  Java 8                          avgt   10  15 811    0 605  us op  9  BufferedReader  JDK                         avgt   10  16 038    0 711  us op  5  parallel Stream Api  Java 8                 avgt   10  21 544    0 583  us op  Performance tests for big String  length   50100   url in github  mode   Average Time  system   Linux  score 200 715 is the best                  Benchmark                        Mode  Cnt   Score        Error  Units  8  ByteArrayOutputStream and read  JDK         avgt   10   200 715      18 103  us op  1  IOUtils toString  Apache Utils              avgt   10   300 019       8 751  us op  6  InputStreamReader and StringBuilder  JDK    avgt   10   347 616     130 348  us op  7  StringWriter and IOUtils copy  Apache       avgt   10   352 791     105 337  us op  2  CharStreams  guava                          avgt   10   420 137      59 877  us op  9  BufferedReader  JDK                         avgt   10   632 028      17 002  us op  5  parallel Stream Api  Java 8                 avgt   10   662 999      46 199  us op  4  Stream Api  Java 8                          avgt   10   701 269      82 296  us op 10  BufferedInputStream  ByteArrayOutputStream  avgt   10   740 837       5 613  us op  3  Scanner  JDK                                avgt   10   751 417      62 026  us op 11  InputStream read   and StringBuilder  JDK   avgt   10  2919 350    1101 942  us op  Graphs  performance tests depending on Input Stream length in Windows 7 system   Performance test  Average Time  depending on Input Stream length in Windows 7 system   length  182    546     1092    3276    9828    29484   58968   test8  0 38    0 938   1 868   4 448   13 412  36 459  72 708  test4  2 362   3 609   5 573   12 769  40 74   81 415  159 864  test5  3 881   5 075   6 904   14 123  50 258  129 937 166 162  test9  2 237   3 493   5 422   11 977  45 98   89 336  177 39  test6  1 261   2 12    4 38    10 698  31 821  86 106  186 636  test7  1 601   2 391   3 646   8 367   38 196  110 221 211 016  test1  1 529   2 381   3 527   8 411   40 551  105 16  212 573  test3  3 035   3 934   8 606   20 858  61 571  118 744 235 428  test2  3 136   6 238   10 508  33 48   43 532  118 044 239 481  test10 1 593   4 736   7 527   20 557  59 856  162 907 323 147  test11 3 913   11 506  23 26   68 644  207 591 600 444 1211 545

User · Answer

public String read InputStream in  throws IOException       try  BufferedReader buffer   new BufferedReader new InputStreamReader in              return buffer lines   collect Collectors joining   n

User · Answer

if You need to convert the string to a specific character set w o external libraries then  public String convertStreamToString InputStream is  throws IOException     try  ByteArrayOutputStream baos   new ByteArrayOutputStream            is transferTo  baos        return baos toString  StandardCharsets UTF 8

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This is an answer adapted from org apache commons io IOUtils source code  for those who want to have the apache implementation but do not want the whole library   private static final int BUFFER SIZE   4   1024   public static String inputStreamToString InputStream inputStream  String charsetName          throws IOException       StringBuilder builder   new StringBuilder        InputStreamReader reader   new InputStreamReader inputStream  charsetName       char   buffer   new char BUFFER SIZE       int length      while   length   reader read buffer      -1            builder append buffer  0  length             return builder toString

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For completeness here is Java 9 solution  public static String toString InputStream input  throws IOException       return new String input readAllBytes    StandardCharsets UTF 8      This uses the readAllBytes method which was added to Java 9

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Here s the most elegant  pure-Java  no library  solution I came up with after some experimentation   public static String fromStream InputStream in  throws IOException       BufferedReader reader   new BufferedReader new InputStreamReader in        StringBuilder out   new StringBuilder        String newLine   System getProperty  line separator        String line      while   line   reader readLine       null            out append line           out append newLine             return out toString

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Use   import java io BufferedInputStream  import java io ByteArrayOutputStream  import java io InputStream  import java io IOException   public static String readInputStreamAsString InputStream in      throws IOException        BufferedInputStream bis   new BufferedInputStream in       ByteArrayOutputStream buf   new ByteArrayOutputStream        int result   bis read        while result    -1          byte b    byte result        buf write b         result   bis read              return buf toString

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I had log4j available  so I was able to use the org apache log4j lf5 util StreamUtils getBytes to get the bytes  which I was able to convert into a string using the String ctor  String result   new String StreamUtils getBytes inputStream

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Make sure to close the streams at end if you use Stream Readers  private String readStream InputStream iStream  throws IOException         build a Stream Reader  it can read char by char     InputStreamReader iStreamReader   new InputStreamReader iStream         build a buffered Reader  so that i can read whole line at once     BufferedReader bReader   new BufferedReader iStreamReader       String line   null      StringBuilder builder   new StringBuilder        while  line   bReader readLine       null       Read till end         builder append line           builder append   n       append new line to preserve lines           bReader close              close all opened stuff     iStreamReader close          iStream close      EDIT  Let the creator of the stream close it                            some readers may auto close the inner stream     return builder toString          EDIT  On JDK 7   you can use try-with-resources construct          Reads the stream into a string     param iStream the input stream     return the string read from the stream     throws IOException when an IO error occurs     private String readStream InputStream iStream  throws IOException          Buffered reader allows us to read line by line     try  BufferedReader bReader                    new BufferedReader new InputStreamReader iStream             StringBuilder builder   new StringBuilder            String line          while  line   bReader readLine       null       Read till end             builder append line               builder append   n       append new line to preserve lines                   return builder toString

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Another one  for all the Spring users   import java nio charset StandardCharsets  import org springframework util FileCopyUtils   public String convertStreamToString InputStream is  throws IOException        return new String FileCopyUtils copyToByteArray is   StandardCharsets UTF 8       The utility methods in org springframework util StreamUtils are similar to the ones in FileCopyUtils  but they leave the stream open when done

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Based on the second part of the accepted Apache Commons answer but with the small gap filled in for always closing the stream       String theString      try           theString   IOUtils toString inputStream  encoding         finally           IOUtils closeQuietly inputStream

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Pure Java solution using Streams  works since Java 8     import java io BufferedReader  import java io IOException  import java io InputStream  import java io InputStreamReader  import java util stream Collectors          public static String inputStreamToString InputStream is  throws IOException       try  BufferedReader br   new BufferedReader new InputStreamReader is              return br lines   collect Collectors joining System lineSeparator                As mentioned by Christoffer Hammarstr  m below other answer it is safer to explicitly specify the Charset  I e  The InputStreamReader constructor can be changes as follows     new InputStreamReader is  Charset forName  UTF-8

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if You need to convert the string to a specific character set w o external libraries then  public String convertStreamToString InputStream is  throws IOException     try  ByteArrayOutputStream baos   new ByteArrayOutputStream            is transferTo  baos        return baos toString  StandardCharsets UTF 8

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Apache Commons allows   String myString   IOUtils toString myInputStream   UTF-8      Of course  you could choose other character encodings besides UTF-8   Also see   documentation

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Here s the most elegant  pure-Java  no library  solution I came up with after some experimentation   public static String fromStream InputStream in  throws IOException       BufferedReader reader   new BufferedReader new InputStreamReader in        StringBuilder out   new StringBuilder        String newLine   System getProperty  line separator        String line      while   line   reader readLine       null            out append line           out append newLine             return out toString

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This snippet was found in  sdk samples android-19 connectivity NetworkConnect NetworkConnectSample src main java com example android networkconnect MainActivity java which is licensed under Apache License  Version 2 0 and written by Google       Reads an InputStream and converts it to a String      param stream InputStream containing HTML from targeted site      param len Length of string that this method returns      return String concatenated according to len parameter      throws java io IOException     throws java io UnsupportedEncodingException     private String readIt InputStream stream  int len  throws IOException  UnsupportedEncodingException       Reader reader   null      reader   new InputStreamReader stream   UTF-8        char   buffer   new char len       reader read buffer       return new String buffer

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ISO-8859-1  Here is a very performant way to do this if you know your input stream s encoding is ISO-8859-1 or ASCII  It  1  avoids the unnecessary synchronization present in StringWriter s internal StringBuffer   2  avoids the overhead of InputStreamReader  and  3  minimizes the number of times StringBuilder s internal char array must be copied   public static String iso 8859 1 InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  chars append  char  buffer i   amp  0xFF                        return chars toString        UTF-8  The same general strategy may be used for a stream encoded with UTF-8    public static String utf8 InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      int state   0      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  if   state   nextStateUtf8 state  buffer i     gt   0                    chars appendCodePoint state                 else if  state    -1      error                 state   0                  chars append   uFFFD      replacement char                                   return chars toString        where the nextStateUtf8   function is defined as follows          Returns the next UTF-8 state given the next byte of input and the current state     If the input byte is the last byte in a valid UTF-8 byte sequence     the returned state will be the corresponding unicode character  in the range of 0 through 0x10FFFF      Otherwise  a negative integer is returned  A state of -1 is returned whenever an    invalid UTF-8 byte sequence is detected      static int nextStateUtf8 int currentState  byte nextByte        switch  currentState  amp  0xF0000000            case 0              if   nextByte  amp  0x80     0      0 trailing bytes  ASCII                  return nextByte                else if   nextByte  amp  0xE0     0xC0      1 trailing byte                 if  nextByte     byte  0xC0    nextByte     byte  0xC1      0xCO  amp  0xC1 are overlong                     return -1                    else                       return nextByte  amp  0xC000001F                                  else if   nextByte  amp  0xF0     0xE0      2 trailing bytes                 if  nextByte     byte  0xE0      possibly overlong                     return nextByte  amp  0xA000000F                    else if  nextByte     byte  0xED      possibly surrogate                     return nextByte  amp  0xB000000F                    else                       return nextByte  amp  0x9000000F                                  else if   nextByte  amp  0xFC     0xF0      3 trailing bytes                 if  nextByte     byte  0xF0      possibly overlong                     return nextByte  amp  0x80000007                    else                       return nextByte  amp  0xE0000007                                  else if  nextByte     byte  0xF4      3 trailing bytes  possibly undefined                 return nextByte  amp  0xD0000007                else                   return -1                        case 0xE0000000    3rd-to-last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0x80000000    3rd-to-last continuation byte  check overlong             return  nextByte  amp  0xE0     0xA0     nextByte  amp  0xF0     0x90   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0xD0000000    3rd-to-last continuation byte  check undefined             return  nextByte  amp  0xF0     0x80   currentState  lt  lt  6   nextByte  amp  0x9000003F   -1          case 0x90000000    2nd-to-last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xA0000000    2nd-to-last continuation byte  check overlong             return  nextByte  amp  0xE0     0xA0   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xB0000000    2nd-to-last continuation byte  check surrogate             return  nextByte  amp  0xE0     0x80   currentState  lt  lt  6   nextByte  amp  0xC000003F   -1          case 0xC0000000    last continuation byte             return  nextByte  amp  0xC0     0x80   currentState  lt  lt  6   nextByte  amp  0x3F   -1          default              return -1            Auto-Detect Encoding  If your input stream was encoded using either ASCII or ISO-8859-1 or UTF-8  but you re not sure which  we can use a similar method to the last  but with an additional encoding-detection component to auto-detect the encoding before returning the string   public static String autoDetect InputStream is  throws IOException       StringBuilder chars   new StringBuilder Math max is available    4096        byte   buffer   new byte 4096       int n      int state   0      boolean ascii   true      while   n   is read buffer      -1            for  int i   0  i  lt  n  i                  if   state   nextStateUtf8 state  buffer i     gt  0x7F                  ascii   false              chars append  char  buffer i   amp  0xFF                         if  ascii    state  lt  0      probably not UTF-8         return chars toString                probably UTF-8     int pos   0      char   charBuf   new char 2       for  int i   0  len   chars length    i  lt  len  i              if   state   nextStateUtf8 state   byte chars charAt i     gt   0                boolean hi   Character toChars state  charBuf  0     2              chars setCharAt pos    charBuf 0                if  hi                    chars setCharAt pos    charBuf 1                                      return chars substring 0  pos       If your input stream has an encoding that is neither ISO-8859-1 nor ASCII nor UTF-8  then I defer to the other answers already present

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InputStream  inputStream   null  BufferedReader bufferedReader   null  try       BufferedReader bufferedReader   new BufferedReader new InputStreamReader inputStream        String stringBuilder   new StringBuilder        String content      while  content   bufferedReader readLine       null           stringBuilder append content             System out println  content of file      stringBuilder toString       catch  IOException e                e printStackTrace             finally                         if bufferedReader    null                   try                      bufferedReader close                     catch IoException ex                      ex printStackTrace

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Use the java io InputStream transferTo OutputStream  supported in Java 9 and the ByteArrayOutputStream toString String  which takes the charset name   public static String gobble InputStream in  String charsetName  throws IOException       ByteArrayOutputStream bos   new ByteArrayOutputStream        in transferTo bos       return bos toString charsetName

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public String read InputStream in  throws IOException       try  BufferedReader buffer   new BufferedReader new InputStreamReader in              return buffer lines   collect Collectors joining   n

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The following doesn t address the original question  but rather some of the responses   Several responses suggest loops of the form  String line   null  while  line   reader readLine       null                 or  for String line   reader readLine    line    null  line   reader readLine                     The first form pollutes the namespace of the enclosing scope by declaring a variable  read  in the enclosing scope that will not be used for anything outside the for loop  The second form duplicates the readline   call   Here is a much cleaner way of writing this sort of loop in Java  It turns out that the first clause in a for-loop doesn t require an actual initializer value  This keeps the scope of the variable  line  to within the body of the for loop  Much more elegant  I haven t seen anybody using this form anywhere  I randomly discovered it one day years ago   but I use it all the time   for  String line   line   reader readLine       null

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Apache Commons allows   String myString   IOUtils toString myInputStream   UTF-8      Of course  you could choose other character encodings besides UTF-8   Also see   documentation

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Taking into account file one should first get a java io Reader instance  This can then be read and added to a StringBuilder  we don t need StringBuffer if we are not accessing it in multiple threads  and StringBuilder is faster   The trick here is that we work in blocks  and as such don t need other buffering streams  The block size is parameterized for run-time performance optimization   public static String slurp final InputStream is  final int bufferSize        final char   buffer   new char bufferSize       final StringBuilder out   new StringBuilder        try  Reader in   new InputStreamReader is   UTF-8              for                    int rsz   in read buffer  0  buffer length               if  rsz  lt  0                  break              out append buffer  0  rsz                       catch  UnsupportedEncodingException ex                                catch  IOException ex                                return out toString

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Taking into account file one should first get a java io Reader instance  This can then be read and added to a StringBuilder  we don t need StringBuffer if we are not accessing it in multiple threads  and StringBuilder is faster   The trick here is that we work in blocks  and as such don t need other buffering streams  The block size is parameterized for run-time performance optimization   public static String slurp final InputStream is  final int bufferSize        final char   buffer   new char bufferSize       final StringBuilder out   new StringBuilder        try  Reader in   new InputStreamReader is   UTF-8              for                    int rsz   in read buffer  0  buffer length               if  rsz  lt  0                  break              out append buffer  0  rsz                       catch  UnsupportedEncodingException ex                                catch  IOException ex                                return out toString

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The easiest way in JDK is with the following code snipplets    String convertToString InputStream in       String resource   new Scanner in  useDelimiter    Z   next        return resource

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A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter    something like  StringWriter writer   new StringWriter    IOUtils copy inputStream  writer  encoding   String theString   writer toString      or even     NB  does not close inputStream  you ll have to use try-with-resources for that String theString   IOUtils toString inputStream  encoding      Alternatively  you could use ByteArrayOutputStream if you don t want to mix your Streams and Writers

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If you can t use Commons IO  FileUtils IOUtils CopyUtils   here s an example using a BufferedReader to read the file line by line   public class StringFromFile       public static void main String   args    throws UnsupportedEncodingException             InputStream is   StringFromFile class getResourceAsStream  file txt            BufferedReader br   new BufferedReader new InputStreamReader is     UTF-8               final int CHARS PER PAGE   5000    counting spaces         StringBuilder builder   new StringBuilder CHARS PER PAGE           try               for String line br readLine    line  null  line br readLine                      builder append line                   builder append   n                                     catch  IOException ignore               String text   builder toString            System out println text             Or if you want raw speed I d propose a variation on what Paul de Vrieze suggested  which avoids using a StringWriter  which uses a StringBuffer internally    public class StringFromFileFast       public static void main String   args    throws UnsupportedEncodingException             InputStream is   StringFromFileFast class getResourceAsStream  file txt            InputStreamReader input   new InputStreamReader is     UTF-8              final int CHARS PER PAGE   5000    counting spaces         final char   buffer   new char CHARS PER PAGE           StringBuilder output   new StringBuilder CHARS PER PAGE           try               for int read   input read buffer  0  buffer length                       read    -1                      read   input read buffer  0  buffer length                     output append buffer  0  read                           catch  IOException ignore               String text   output toString            System out println text

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If you are using Google-Collections Guava you could do the following   InputStream stream       String content   CharStreams toString new InputStreamReader stream  Charsets UTF 8    Closeables closeQuietly stream     Note that the second parameter  i e  Charsets UTF 8  for the InputStreamReader isn t necessary  but it is generally a good idea to specify the encoding if you know it  which you should

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Here s a way using only the standard Java library  note that the stream is not closed  your mileage may vary    static String convertStreamToString java io InputStream is        java util Scanner s   new java util Scanner is  useDelimiter    A        return s hasNext     s next             I learned this trick from  Stupid Scanner tricks  article  The reason it works is because Scanner iterates over tokens in the stream  and in this case we separate tokens using  beginning of the input boundary    A   thus giving us only one token for the entire contents of the stream   Note  if you need to be specific about the input stream s encoding  you can provide the second argument to Scanner constructor that indicates what character set to use  e g   UTF-8     Hat tip goes also to Jacob  who once pointed me to the said article

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Guava provides much shorter efficient autoclosing solution in case when input stream comes from classpath resource  which seems to be popular task    byte   bytes   Resources toByteArray classLoader getResource path      or   String text   Resources toString classLoader getResource path   StandardCharsets UTF 8     There is also general concept of ByteSource and CharSource that gently take care of both opening and closing the stream   So  for example  instead of explicitly opening a small file to read its contents   String content   Files asCharSource new File  robots txt    StandardCharsets UTF 8  read    byte   data   Files asByteSource new File  favicon ico    read      or just  String content   Files toString new File  robots txt    StandardCharsets UTF 8   byte   data   Files toByteArray new File  favicon ico

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This is the best pure Java solution that fits perfectly for Android and any other JVM   This solution works amazingly well    it is simple  fast  and works on small and large streams just the same    see benchmark above   No  8   public String readFullyAsString InputStream inputStream  String encoding          throws IOException       return readFully inputStream  toString encoding      public byte   readFullyAsBytes InputStream inputStream          throws IOException       return readFully inputStream  toByteArray       private ByteArrayOutputStream readFully InputStream inputStream          throws IOException       ByteArrayOutputStream baos   new ByteArrayOutputStream        byte   buffer   new byte 1024       int length   0      while   length   inputStream read buffer      -1            baos write buffer  0  length             return baos

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This solution to this question is not the simplest  but since NIO streams and channels have not been mentioned  here goes a version which uses NIO channels and a ByteBuffer to convert a stream into a string   public static String streamToStringChannel InputStream in  String encoding  int bufSize  throws IOException       ReadableByteChannel channel   Channels newChannel in       ByteBuffer byteBuffer   ByteBuffer allocate bufSize       ByteArrayOutputStream bout   new ByteArrayOutputStream        WritableByteChannel outChannel   Channels newChannel bout       while  channel read byteBuffer   gt  0    byteBuffer position    gt  0            byteBuffer flip       make buffer ready for write         outChannel write byteBuffer           byteBuffer compact      make buffer ready for reading           channel close        outChannel close        return bout toString encoding       Here is an example how to use it   try  InputStream in   new FileInputStream   tmp large file xml          String x   streamToStringChannel in   UTF-8   1       System out println x       The performance of this method should be good for large files

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If you are using Google-Collections Guava you could do the following   InputStream stream       String content   CharStreams toString new InputStreamReader stream  Charsets UTF 8    Closeables closeQuietly stream     Note that the second parameter  i e  Charsets UTF 8  for the InputStreamReader isn t necessary  but it is generally a good idea to specify the encoding if you know it  which you should

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Based on the second part of the accepted Apache Commons answer but with the small gap filled in for always closing the stream       String theString      try           theString   IOUtils toString inputStream  encoding         finally           IOUtils closeQuietly inputStream

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Quick and easy   String result    String new ObjectInputStream  inputStream   readObject

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Pure Java solution using Streams  works since Java 8     import java io BufferedReader  import java io IOException  import java io InputStream  import java io InputStreamReader  import java util stream Collectors          public static String inputStreamToString InputStream is  throws IOException       try  BufferedReader br   new BufferedReader new InputStreamReader is              return br lines   collect Collectors joining System lineSeparator                As mentioned by Christoffer Hammarstr  m below other answer it is safer to explicitly specify the Charset  I e  The InputStreamReader constructor can be changes as follows     new InputStreamReader is  Charset forName  UTF-8

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The below code worked for me    URL url   MyClass class getResource       configFileName   BufferedInputStream bi    BufferedInputStream  url getContent    byte   buffer   new byte bi available      int bytesRead   bi read buffer   String out   new String buffer     Please note  according to Java docs  the available   method might not work with InputStream but always works with BufferedInputStream  In case you don t want to use available   method we can always use the below code  URL url   MyClass class getResource       configFileName   BufferedInputStream bi    BufferedInputStream  url getContent    File f   new File url getPath     byte   buffer   new byte   int  f length     int bytesRead   bi read buffer   String out   new String buffer     I am not sure if there will be any encoding issues  Please comment  if there will be any issues with the code

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String inputStreamToString InputStream inputStream  Charset charset  throws IOException       try               final StringWriter writer   new StringWriter                final InputStreamReader reader   new InputStreamReader inputStream  charset                      reader transferTo writer           return writer toString               pure Java standard library solution - no libs since Java 10 - Reader transferTo java io Writer  loopless solution no new line character handling

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In Groovy  inputStream getText

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With Okio   String result   Okio buffer Okio source inputStream   readUtf8

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The below code worked for me    URL url   MyClass class getResource       configFileName   BufferedInputStream bi    BufferedInputStream  url getContent    byte   buffer   new byte bi available      int bytesRead   bi read buffer   String out   new String buffer     Please note  according to Java docs  the available   method might not work with InputStream but always works with BufferedInputStream  In case you don t want to use available   method we can always use the below code  URL url   MyClass class getResource       configFileName   BufferedInputStream bi    BufferedInputStream  url getContent    File f   new File url getPath     byte   buffer   new byte   int  f length     int bytesRead   bi read buffer   String out   new String buffer     I am not sure if there will be any encoding issues  Please comment  if there will be any issues with the code

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Taking into account file one should first get a java io Reader instance  This can then be read and added to a StringBuilder  we don t need StringBuffer if we are not accessing it in multiple threads  and StringBuilder is faster   The trick here is that we work in blocks  and as such don t need other buffering streams  The block size is parameterized for run-time performance optimization   public static String slurp final InputStream is  final int bufferSize        final char   buffer   new char bufferSize       final StringBuilder out   new StringBuilder        try  Reader in   new InputStreamReader is   UTF-8              for                    int rsz   in read buffer  0  buffer length               if  rsz  lt  0                  break              out append buffer  0  rsz                       catch  UnsupportedEncodingException ex                                catch  IOException ex                                return out toString

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Another one  for all the Spring users   import java nio charset StandardCharsets  import org springframework util FileCopyUtils   public String convertStreamToString InputStream is  throws IOException        return new String FileCopyUtils copyToByteArray is   StandardCharsets UTF 8       The utility methods in org springframework util StreamUtils are similar to the ones in FileCopyUtils  but they leave the stream open when done

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I did a benchmark upon 14 distinct answers here  sorry for not providing credits but there are too many duplicates    The result is very surprising  It turns out that Apache IOUtils is the slowest and ByteArrayOutputStream is the fastest solutions   So first here is the best method   public String inputStreamToString InputStream inputStream  throws IOException       try ByteArrayOutputStream result   new ByteArrayOutputStream              byte   buffer   new byte 1024           int length          while   length   inputStream read buffer      -1                result write buffer  0  length                      return result toString UTF 8             Benchmark results  of 20 MB random bytes in 20 cycles  Time in milliseconds   ByteArrayOutputStreamTest  194 NioStream  198 Java9ISTransferTo  201 Java9ISReadAllBytes  205 BufferedInputStreamVsByteArrayOutputStream  314 ApacheStringWriter2  574 GuavaCharStreams  589 ScannerReaderNoNextTest  614 ScannerReader  633 ApacheStringWriter  1544 StreamApi  Error ParallelStreamApi  Error BufferReaderTest  Error InputStreamAndStringBuilder  Error   Benchmark source code  import com google common io CharStreams  import org apache commons io IOUtils   import java io    import java nio ByteBuffer  import java nio channels Channels  import java nio channels ReadableByteChannel  import java nio channels WritableByteChannel  import java util Arrays  import java util List  import java util Random  import java util stream Collectors          Created by Ilya Gazman on 2 13 18      public class InputStreamToString         private static final String UTF 8    UTF-8        public static void main String    args            log  App started            byte   bytes   new byte 1024   1024           new Random   nextBytes bytes           log  Stream is ready n             try               test bytes             catch  IOException e                e printStackTrace                         private static void test byte   bytes  throws IOException           List lt Stringify gt  tests   Arrays asList                  new ApacheStringWriter                    new ApacheStringWriter2                    new NioStream                    new ScannerReader                    new ScannerReaderNoNextTest                    new GuavaCharStreams                    new StreamApi                    new ParallelStreamApi                    new ByteArrayOutputStreamTest                    new BufferReaderTest                    new BufferedInputStreamVsByteArrayOutputStream                    new InputStreamAndStringBuilder                    new Java9ISTransferTo                    new Java9ISReadAllBytes                       String solution   new String bytes   UTF-8             for  Stringify test   tests                try  ByteArrayInputStream inputStream   new ByteArrayInputStream bytes                     String s   test inputStreamToString inputStream                   if   s equals solution                         log test name        Error                        continue                                              long startTime   System currentTimeMillis                for  int i   0  i  lt  20  i                      try  ByteArrayInputStream inputStream   new ByteArrayInputStream bytes                         test inputStreamToString inputStream                                               log test name             System currentTimeMillis   - startTime                         private static void log String message            System out println message              interface Stringify           String inputStreamToString InputStream inputStream  throws IOException           default String name                 return this getClass   getSimpleName                         static class ApacheStringWriter implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               StringWriter writer   new StringWriter                IOUtils copy inputStream  writer  UTF 8               return writer toString                         static class ApacheStringWriter2 implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return IOUtils toString inputStream  UTF 8                        static class NioStream implements Stringify             Override         public String inputStreamToString InputStream in  throws IOException               ReadableByteChannel channel   Channels newChannel in               ByteBuffer byteBuffer   ByteBuffer allocate 1024   16               ByteArrayOutputStream bout   new ByteArrayOutputStream                WritableByteChannel outChannel   Channels newChannel bout               while  channel read byteBuffer   gt  0    byteBuffer position    gt  0                    byteBuffer flip       make buffer ready for write                 outChannel write byteBuffer                   byteBuffer compact      make buffer ready for reading                           channel close                outChannel close                return bout toString UTF 8                        static class ScannerReader implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               java util Scanner s   new java util Scanner is  useDelimiter    A                return s hasNext     s next                              static class ScannerReaderNoNextTest implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               java util Scanner s   new java util Scanner is  useDelimiter    A                return s next                         static class GuavaCharStreams implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               return CharStreams toString new InputStreamReader                      is  UTF 8                         static class StreamApi implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new BufferedReader new InputStreamReader inputStream                        lines   collect Collectors joining   n                          static class ParallelStreamApi implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new BufferedReader new InputStreamReader inputStream   lines                        parallel   collect Collectors joining   n                          static class ByteArrayOutputStreamTest implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               try ByteArrayOutputStream result   new ByteArrayOutputStream                      byte   buffer   new byte 1024                   int length                  while   length   inputStream read buffer      -1                        result write buffer  0  length                                      return result toString UTF 8                                      static class BufferReaderTest implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               String newLine   System getProperty  line separator                BufferedReader reader   new BufferedReader new InputStreamReader inputStream                StringBuilder result   new StringBuilder UTF 8               String line              boolean flag   false              while   line   reader readLine       null                    result append flag   newLine       append line                   flag   true                            return result toString                         static class BufferedInputStreamVsByteArrayOutputStream implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               BufferedInputStream bis   new BufferedInputStream inputStream               ByteArrayOutputStream buf   new ByteArrayOutputStream                int result   bis read                while  result    -1                    buf write  byte  result                   result   bis read                               return buf toString UTF 8                        static class InputStreamAndStringBuilder implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               int ch              StringBuilder sb   new StringBuilder UTF 8               while   ch   inputStream read       -1                  sb append  char  ch               return sb toString                         static class Java9ISTransferTo implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               ByteArrayOutputStream bos   new ByteArrayOutputStream                inputStream transferTo bos               return bos toString UTF 8                        static class Java9ISReadAllBytes implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new String inputStream readAllBytes    UTF 8

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Method to convert inputStream to String  public static String getStringFromInputStream InputStream inputStream         BufferedReader bufferedReader   null      StringBuilder stringBuilder   new StringBuilder        String line       try           bufferedReader   new BufferedReader new InputStreamReader                  inputStream            while   line   bufferedReader readLine       null                stringBuilder append line                   catch  IOException e            logger error e getMessage           finally           if  bufferedReader    null                try                   bufferedReader close                  catch  IOException e                    logger error e getMessage                                       return stringBuilder toString

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In terms of reduce  and concat it can be expressed in Java 8 as   String fromFile   new BufferedReader new    InputStreamReader inputStream   lines   reduce String  concat  get

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Use   InputStream in      Your InputStream     StringBuilder sb   new StringBuilder    BufferedReader br   new BufferedReader new InputStreamReader in    String read   while   read br readLine       null          System out println read       sb append read      br close    return sb toString

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You can use Apache Commons   In the IOUtils you can find the toString method with three helpful implementations   public static String toString InputStream input  throws IOException           return toString input  Charset defaultCharset        public static String toString InputStream input  throws IOException           return toString input  Charset defaultCharset        public static String toString InputStream input  String encoding              throws IOException           return toString input  Charsets toCharset encoding

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InputStream IS new URL  http   www petrol si api gas prices json   openStream          ByteArrayOutputStream BAOS new ByteArrayOutputStream      IOUtils copy IS  BAOS     String d  new String BAOS toByteArray    UTF-8                System out println d

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A nice way to do this is using Apache commons IOUtils to copy the InputStream into a StringWriter    something like  StringWriter writer   new StringWriter    IOUtils copy inputStream  writer  encoding   String theString   writer toString      or even     NB  does not close inputStream  you ll have to use try-with-resources for that String theString   IOUtils toString inputStream  encoding      Alternatively  you could use ByteArrayOutputStream if you don t want to mix your Streams and Writers

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I ran some timing tests because time matters  always   I attempted to get the response into a String 3 different ways   shown below  I left out try catch blocks for the sake readability   To give context  this is the preceding code for all 3 approaches      String response     String url    www blah com path key value      GetMethod method   new GetMethod url      int status   client executeMethod method     1    response   method getResponseBodyAsString      2   InputStream resp   method getResponseBodyAsStream    InputStreamReader is new InputStreamReader resp   BufferedReader br new BufferedReader is   String read   null  StringBuffer sb   new StringBuffer    while  read   br readLine       null        sb append read     response   sb toString      3   InputStream iStream    method getResponseBodyAsStream    StringWriter writer   new StringWriter    IOUtils copy iStream  writer   UTF-8    response   writer toString      So  after running 500 tests on each approach with the same request response data  here are the numbers  Once again  these are my findings and your findings may not be exactly the same  but I wrote this to give some indication to others of the efficiency differences of these approaches   Ranks  Approach  1 Approach  3 - 2 6  slower than  1 Approach  2 - 4 3  slower than  1  Any of these approaches is an appropriate solution for grabbing a response and creating a String from it

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Also you can get InputStream from a specified resource path   public static InputStream getResourceAsStream String path        InputStream myiInputStream   ClassName class getResourceAsStream path       if  null    myiInputStream                mylogger info  Can t find path      path              return myiInputStream      To get InputStream from a specific path   public static URL getResource String path        URL myURL   ClassName class getResource path       if  null    myURL                mylogger info  Can t find resource path      path             return myURL

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JDK 7 8 answer that closes the stream and still throws an IOException   StringBuilder build   new StringBuilder    byte   buf   new byte 1024   int length  try  InputStream is   getInputStream        while   length   is read buf      -1        build append new String buf  0  length

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Kotlin users simply do   println InputStreamReader is  readText      whereas   readText     is Kotlin standard library   s built-in extension method

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This is the best pure Java solution that fits perfectly for Android and any other JVM   This solution works amazingly well    it is simple  fast  and works on small and large streams just the same    see benchmark above   No  8   public String readFullyAsString InputStream inputStream  String encoding          throws IOException       return readFully inputStream  toString encoding      public byte   readFullyAsBytes InputStream inputStream          throws IOException       return readFully inputStream  toByteArray       private ByteArrayOutputStream readFully InputStream inputStream          throws IOException       ByteArrayOutputStream baos   new ByteArrayOutputStream        byte   buffer   new byte 1024       int length   0      while   length   inputStream read buffer      -1            baos write buffer  0  length             return baos

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InputStream is   Context openFileInput someFileName      whatever format you have  ByteArrayOutputStream bos   new ByteArrayOutputStream     byte   b   new byte 8192   for  int bytesRead   bytesRead   is read b      -1         bos write b  0  bytesRead      String output   bos toString someEncoding

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Note  This probably isn t a good idea  This method uses recursion and thus will hit a StackOverflowError very quickly   public String read  InputStream is        byte next   is read        return next    -1        next   read is      Recursive part  reads next byte recursively     Please don t downvote this just because it s a bad choice to use  this was mostly creative

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If you were feeling adventurous  you could mix Scala and Java and end up with this   scala io Source fromInputStream is  mkString       Mixing Java and Scala code and libraries has it s benefits   See full description here  Idiomatic way to convert an InputStream to a String in Scala

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InputStreamReader i   new InputStreamReader s   BufferedReader str   new BufferedReader i   String msg   str readLine    System out println msg     Here s is your InputStream object which will get convert into String

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Well  you can program it for yourself    It s not complicated     String Inputstream2String  InputStream is  throws IOException               final int PKG SIZE   1024          byte   data   new byte  PKG SIZE           StringBuilder buffer   new StringBuilder PKG SIZE   10           int size           size   is read data  0  data length           while  size  gt  0                        String str   new String data  0  size               buffer append str               size   is read data  0  data length                     return buffer toString

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Try these 4 statements    As per the point recalled by Fred  it is not recommended to append a String with    operator since every time a new char is appended to the existing String creating a new String object again and assigning its address to st while the old st object becomes garbage   public String convertStreamToString InputStream is        int k      StringBuffer sb new StringBuffer        while  k fin read       -1                sb append  char k             return sb toString          Not recommended  but this is also a way  public String convertStreamToString InputStream is         int k      String st         while  k is read       -1                st   char k            return st

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I had log4j available  so I was able to use the org apache log4j lf5 util StreamUtils getBytes to get the bytes  which I was able to convert into a string using the String ctor  String result   new String StreamUtils getBytes inputStream

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Make sure to close the streams at end if you use Stream Readers  private String readStream InputStream iStream  throws IOException         build a Stream Reader  it can read char by char     InputStreamReader iStreamReader   new InputStreamReader iStream         build a buffered Reader  so that i can read whole line at once     BufferedReader bReader   new BufferedReader iStreamReader       String line   null      StringBuilder builder   new StringBuilder        while  line   bReader readLine       null       Read till end         builder append line           builder append   n       append new line to preserve lines           bReader close              close all opened stuff     iStreamReader close          iStream close      EDIT  Let the creator of the stream close it                            some readers may auto close the inner stream     return builder toString          EDIT  On JDK 7   you can use try-with-resources construct          Reads the stream into a string     param iStream the input stream     return the string read from the stream     throws IOException when an IO error occurs     private String readStream InputStream iStream  throws IOException          Buffered reader allows us to read line by line     try  BufferedReader bReader                    new BufferedReader new InputStreamReader iStream             StringBuilder builder   new StringBuilder            String line          while  line   bReader readLine       null       Read till end             builder append line               builder append   n       append new line to preserve lines                   return builder toString

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Here s a way using only the standard Java library  note that the stream is not closed  your mileage may vary    static String convertStreamToString java io InputStream is        java util Scanner s   new java util Scanner is  useDelimiter    A        return s hasNext     s next             I learned this trick from  Stupid Scanner tricks  article  The reason it works is because Scanner iterates over tokens in the stream  and in this case we separate tokens using  beginning of the input boundary    A   thus giving us only one token for the entire contents of the stream   Note  if you need to be specific about the input stream s encoding  you can provide the second argument to Scanner constructor that indicates what character set to use  e g   UTF-8     Hat tip goes also to Jacob  who once pointed me to the said article

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This snippet was found in  sdk samples android-19 connectivity NetworkConnect NetworkConnectSample src main java com example android networkconnect MainActivity java which is licensed under Apache License  Version 2 0 and written by Google       Reads an InputStream and converts it to a String      param stream InputStream containing HTML from targeted site      param len Length of string that this method returns      return String concatenated according to len parameter      throws java io IOException     throws java io UnsupportedEncodingException     private String readIt InputStream stream  int len  throws IOException  UnsupportedEncodingException       Reader reader   null      reader   new InputStreamReader stream   UTF-8        char   buffer   new char len       reader read buffer       return new String buffer

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Kotlin users simply do   println InputStreamReader is  readText      whereas   readText     is Kotlin standard library   s built-in extension method

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For completeness here is Java 9 solution  public static String toString InputStream input  throws IOException       return new String input readAllBytes    StandardCharsets UTF 8      This uses the readAllBytes method which was added to Java 9

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Here s more-or-less sampath s answer  cleaned up a bit and represented as a function   String streamToString InputStream in  throws IOException     StringBuilder out   new StringBuilder      BufferedReader br   new BufferedReader new InputStreamReader in      for String line   br readLine    line    null  line   br readLine         out append line     br close      return out toString

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Raghu K Nair Was the only one using a scanner  The code I use is a little different   String convertToString InputStream in       Scanner scanner   new Scanner in      scanner useDelimiter    A         boolean hasInput   scanner hasNext        if  hasInput            return scanner next          else           return null             About Delimiters  How do I use a delimiter in Java Scanner

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The easiest way in JDK is with the following code snipplets    String convertToString InputStream in       String resource   new Scanner in  useDelimiter    Z   next        return resource

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Try these 4 statements    As per the point recalled by Fred  it is not recommended to append a String with    operator since every time a new char is appended to the existing String creating a new String object again and assigning its address to st while the old st object becomes garbage   public String convertStreamToString InputStream is        int k      StringBuffer sb new StringBuffer        while  k fin read       -1                sb append  char k             return sb toString          Not recommended  but this is also a way  public String convertStreamToString InputStream is         int k      String st         while  k is read       -1                st   char k            return st

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Here is the complete method for converting InputStream into String without using any third party library  Use StringBuilder for single threaded environment otherwise use StringBuffer     public static String getString  InputStream is  throws IOException       int ch      StringBuilder sb   new StringBuilder        while  ch   is read       -1          sb append  char ch       return sb toString

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I did a benchmark upon 14 distinct answers here  sorry for not providing credits but there are too many duplicates    The result is very surprising  It turns out that Apache IOUtils is the slowest and ByteArrayOutputStream is the fastest solutions   So first here is the best method   public String inputStreamToString InputStream inputStream  throws IOException       try ByteArrayOutputStream result   new ByteArrayOutputStream              byte   buffer   new byte 1024           int length          while   length   inputStream read buffer      -1                result write buffer  0  length                      return result toString UTF 8             Benchmark results  of 20 MB random bytes in 20 cycles  Time in milliseconds   ByteArrayOutputStreamTest  194 NioStream  198 Java9ISTransferTo  201 Java9ISReadAllBytes  205 BufferedInputStreamVsByteArrayOutputStream  314 ApacheStringWriter2  574 GuavaCharStreams  589 ScannerReaderNoNextTest  614 ScannerReader  633 ApacheStringWriter  1544 StreamApi  Error ParallelStreamApi  Error BufferReaderTest  Error InputStreamAndStringBuilder  Error   Benchmark source code  import com google common io CharStreams  import org apache commons io IOUtils   import java io    import java nio ByteBuffer  import java nio channels Channels  import java nio channels ReadableByteChannel  import java nio channels WritableByteChannel  import java util Arrays  import java util List  import java util Random  import java util stream Collectors          Created by Ilya Gazman on 2 13 18      public class InputStreamToString         private static final String UTF 8    UTF-8        public static void main String    args            log  App started            byte   bytes   new byte 1024   1024           new Random   nextBytes bytes           log  Stream is ready n             try               test bytes             catch  IOException e                e printStackTrace                         private static void test byte   bytes  throws IOException           List lt Stringify gt  tests   Arrays asList                  new ApacheStringWriter                    new ApacheStringWriter2                    new NioStream                    new ScannerReader                    new ScannerReaderNoNextTest                    new GuavaCharStreams                    new StreamApi                    new ParallelStreamApi                    new ByteArrayOutputStreamTest                    new BufferReaderTest                    new BufferedInputStreamVsByteArrayOutputStream                    new InputStreamAndStringBuilder                    new Java9ISTransferTo                    new Java9ISReadAllBytes                       String solution   new String bytes   UTF-8             for  Stringify test   tests                try  ByteArrayInputStream inputStream   new ByteArrayInputStream bytes                     String s   test inputStreamToString inputStream                   if   s equals solution                         log test name        Error                        continue                                              long startTime   System currentTimeMillis                for  int i   0  i  lt  20  i                      try  ByteArrayInputStream inputStream   new ByteArrayInputStream bytes                         test inputStreamToString inputStream                                               log test name             System currentTimeMillis   - startTime                         private static void log String message            System out println message              interface Stringify           String inputStreamToString InputStream inputStream  throws IOException           default String name                 return this getClass   getSimpleName                         static class ApacheStringWriter implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               StringWriter writer   new StringWriter                IOUtils copy inputStream  writer  UTF 8               return writer toString                         static class ApacheStringWriter2 implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return IOUtils toString inputStream  UTF 8                        static class NioStream implements Stringify             Override         public String inputStreamToString InputStream in  throws IOException               ReadableByteChannel channel   Channels newChannel in               ByteBuffer byteBuffer   ByteBuffer allocate 1024   16               ByteArrayOutputStream bout   new ByteArrayOutputStream                WritableByteChannel outChannel   Channels newChannel bout               while  channel read byteBuffer   gt  0    byteBuffer position    gt  0                    byteBuffer flip       make buffer ready for write                 outChannel write byteBuffer                   byteBuffer compact      make buffer ready for reading                           channel close                outChannel close                return bout toString UTF 8                        static class ScannerReader implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               java util Scanner s   new java util Scanner is  useDelimiter    A                return s hasNext     s next                              static class ScannerReaderNoNextTest implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               java util Scanner s   new java util Scanner is  useDelimiter    A                return s next                         static class GuavaCharStreams implements Stringify             Override         public String inputStreamToString InputStream is  throws IOException               return CharStreams toString new InputStreamReader                      is  UTF 8                         static class StreamApi implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new BufferedReader new InputStreamReader inputStream                        lines   collect Collectors joining   n                          static class ParallelStreamApi implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new BufferedReader new InputStreamReader inputStream   lines                        parallel   collect Collectors joining   n                          static class ByteArrayOutputStreamTest implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               try ByteArrayOutputStream result   new ByteArrayOutputStream                      byte   buffer   new byte 1024                   int length                  while   length   inputStream read buffer      -1                        result write buffer  0  length                                      return result toString UTF 8                                      static class BufferReaderTest implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               String newLine   System getProperty  line separator                BufferedReader reader   new BufferedReader new InputStreamReader inputStream                StringBuilder result   new StringBuilder UTF 8               String line              boolean flag   false              while   line   reader readLine       null                    result append flag   newLine       append line                   flag   true                            return result toString                         static class BufferedInputStreamVsByteArrayOutputStream implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               BufferedInputStream bis   new BufferedInputStream inputStream               ByteArrayOutputStream buf   new ByteArrayOutputStream                int result   bis read                while  result    -1                    buf write  byte  result                   result   bis read                               return buf toString UTF 8                        static class InputStreamAndStringBuilder implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               int ch              StringBuilder sb   new StringBuilder UTF 8               while   ch   inputStream read       -1                  sb append  char  ch               return sb toString                         static class Java9ISTransferTo implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               ByteArrayOutputStream bos   new ByteArrayOutputStream                inputStream transferTo bos               return bos toString UTF 8                        static class Java9ISReadAllBytes implements Stringify             Override         public String inputStreamToString InputStream inputStream  throws IOException               return new String inputStream readAllBytes    UTF 8

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Here s how to do it using just the JDK using byte array buffers  This is actually how the commons-io IOUtils copy   methods all work  You can replace byte   with char   if you re copying from a Reader instead of an InputStream   import java io ByteArrayOutputStream  import java io InputStream        InputStream is        ByteArrayOutputStream baos   new ByteArrayOutputStream 8192   byte   buffer   new byte 8192   int count   0  try     while   count   is read buffer      -1        baos write buffer  0  count         finally     try       is close          catch  Exception ignore           String charset    UTF-8   String inputStreamAsString   baos toString charset

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Raghu K Nair Was the only one using a scanner  The code I use is a little different   String convertToString InputStream in       Scanner scanner   new Scanner in      scanner useDelimiter    A         boolean hasInput   scanner hasNext        if  hasInput            return scanner next          else           return null             About Delimiters  How do I use a delimiter in Java Scanner

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Guava provides much shorter efficient autoclosing solution in case when input stream comes from classpath resource  which seems to be popular task    byte   bytes   Resources toByteArray classLoader getResource path      or   String text   Resources toString classLoader getResource path   StandardCharsets UTF 8     There is also general concept of ByteSource and CharSource that gently take care of both opening and closing the stream   So  for example  instead of explicitly opening a small file to read its contents   String content   Files asCharSource new File  robots txt    StandardCharsets UTF 8  read    byte   data   Files asByteSource new File  favicon ico    read      or just  String content   Files toString new File  robots txt    StandardCharsets UTF 8   byte   data   Files toByteArray new File  favicon ico

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I have written a class that does just that  so I figured I d share it with everyone  Sometimes you don t want to add Apache Commons just for one thing  and want something dumber than Scanner that doesn t examine the content   Usage is as follows     Read from InputStream String data   new ReaderSink inputStream  Charset forName  UTF-8    drain        Read from File data   new ReaderSink file  Charset forName  UTF-8    drain        Drain input stream to console new ReaderSink inputStream  Charset forName  UTF-8    drainTo System out     Here is the code for ReaderSink   import java io    import java nio charset Charset          A simple sink class that drains a   link Reader  to a   link String  or    to a   link Writer          author Ben Barkay     version 2 20 2014     public class ReaderSink                  The default buffer size to use if no buffer size was specified              public static final int DEFAULT BUFFER SIZE   1024                  The   link Reader  that will be drained              private final Reader in                  Constructs a new   code ReaderSink  for the specified file and charset          param file      The file to read from          param charset   The charset to use          throws FileNotFoundException    If the file was not found on the filesystem              public ReaderSink File file  Charset charset  throws FileNotFoundException           this new FileInputStream file   charset                         Constructs a new   code ReaderSink  for the specified   link InputStream           param in        The   link InputStream  to drain          param charset   The charset to use              public ReaderSink InputStream in  Charset charset            this new InputStreamReader in  charset                          Constructs a new   code ReaderSink  for the specified   link Reader           param in    The reader to drain              public ReaderSink Reader in            this in   in                        Drains the data from the underlying   link Reader   returning a   link String  containing        all of the read information  This method will use   link  DEFAULT BUFFER SIZE  for        its buffer size          return  A   link String  containing all of the information that was read              public String drain   throws IOException           return drain DEFAULT BUFFER SIZE                         Drains the data from the underlying   link Reader   returning a   link String  containing        all of the read information          param bufferSize    The size of the buffer to use when reading          return  A   link String  containing all of the information that was read              public String drain int bufferSize  throws IOException           StringWriter stringWriter   new StringWriter            drainTo stringWriter  bufferSize           return stringWriter toString                          Drains the data from the underlying   link Reader   writing it to the        specified   link Writer   This method will use   link  DEFAULT BUFFER SIZE  for        its buffer size          param out   The   link Writer  to write to              public void drainTo Writer out  throws IOException           drainTo out  DEFAULT BUFFER SIZE                         Drains the data from the underlying   link Reader   writing it to the        specified   link Writer           param out           The   link Writer  to write to          param bufferSize    The size of the buffer to use when reader              public void drainTo Writer out  int bufferSize  throws IOException           char   buffer   new char bufferSize           int read          while   read   in read buffer    gt  -1                out write buffer  0  read

[java] How do I read / convert an InputStream into a String in Java?

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