What is simplest way to read a file into String

Question

I am trying to read a simple text file into a String  Of course there is the usual way of getting the input stream and iterating with readLine   and reading contents into String    Having done this hundreds of times in past  I just wondered how can I do this in minimum lines of code  Isn t there something in java like String fileContents   XXX readFile myFile  File       rather anything that looks as simple as this   I know there are libraries like Apache Commons IO which provide such simplifications or even I can write a simple Util class to do this  But all that I wonder is - this is a so frequent operation that everyone needs then why doesn t Java provide such simple function  Isn t there really a single method somewhere to read a file into string with some default or specified encoding

User · Accepted Answer

Yes  you can do this in one line  though for robust IOException handling you wouldn t want to    String content   new Scanner new File  filename    useDelimiter    Z   next    System out println content     This uses a java util Scanner  telling it to delimit the input with  Z  which is the end of the string anchor  This ultimately makes the input have one actual token  which is the entire file  so it can be read with one call to next     There is a constructor that takes a File and a String charSetName  among many other overloads   These two constructor may throw FileNotFoundException  but like all Scanner methods  no IOException can be thrown beyond these constructors   You can query the Scanner itself through the ioException   method if an IOException occurred or not  You may also want to explicitly close   the Scanner after you read the content  so perhaps storing the Scanner reference in a local variable is best   See also   Java Tutorials - I O Essentials - Scanning and formatting   Related questions   Validating input using java util Scanner - has many examples of more typical usage     Third-party library options  For completeness  these are some really good options if you have these very reputable and highly useful third party libraries   Guava  com google common io Files contains many useful methods  The pertinent ones here are    String toString File  Charset    Using the given character set  reads all characters from a file into a String  List lt String gt  readLines File  Charset        reads all of the lines from a file into a List lt String gt   one entry per line    Apache Commons IO  org apache commons io IOUtils also offer similar functionality    String toString InputStream  String encoding    Using the specified character encoding  gets the contents of an InputStream as a String   List readLines InputStream  String encoding        as a  raw  List of String  one entry per line    Related questions   Most useful free third party Java libraries  deleted

User · Answer

From Java 7  API Description  onwards you can do   new String Files readAllBytes Paths get filePath    StandardCharsets UTF 8    Where filePath is a String representing the file you want to load

User · Answer

Sadly  no   I agree that such frequent operation should have easier implementation than copying of input line by line in loop  but you ll have to either write helper method or use external library

User · Answer

Don t write your own util class to do this - I would recommend using Guava  which is full of all kinds of goodness  In this case you d want either the Files class  if you re really just reading a file  or CharStreams for more general purpose reading  It has methods to read the data into a list of strings  readLines  or totally  toString    It has similar useful methods for binary data too  And then there s the rest of the library     I agree it s annoying that there s nothing similar in the standard libraries  Heck  just being able to supply a CharSet to a FileReader would make life a little simpler

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Another alternative approach is   How do I create a Java string from the contents of a file   Other option is to use utilities provided open source libraries   http   commons apache org io api-1 4 index html org apache commons io IOUtils html  Why java doesn t provide such a common util API   a  to keep the APIs generic so that encoding  buffering etc is handled by the programmer  b  make programmers do some work  and write share opensource util libraries  D  -

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This should work for you   import java io IOException  import java nio file Files  import java nio file Paths   public static void main String   args  throws IOException       String content   new String Files readAllBytes Paths get  abc java

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I discovered that the accepted answer actually doesn t always work  because   Z may occur in the file  Another problem is that if you don t have the correct charset a whole bunch of unexpected things may happen which may cause the scanner to read only a part of the file   The solution is to use a delimiter which you are certain will never occur in the file  However  this is theoretically impossible  What we CAN do  is use a delimiter that has such a small chance to occur in the file that it is negligible  such a delimiter is a UUID  which is natively supported in Java   String content   new Scanner file   UTF-8        useDelimiter UUID randomUUID   toString    next

User · Answer

You can use apache commons IO    FileInputStream fisTargetFile   new FileInputStream new File  test txt      String targetFileStr   IOUtils toString fisTargetFile   UTF-8

User · Answer

Using Apache Commons IO   import org apache commons io FileUtils          String contents   FileUtils readFileToString new File   path to the file     UTF-8     You can see de javadoc for the method for details

[java] What is simplest way to read a file into String?

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