Android Reading from an Input stream efficiently

Question

I am making an HTTP get request to a website for an android application I am making   I am using a DefaultHttpClient and using HttpGet to issue the request  I get the entity response and from this obtain an InputStream object for getting the html of the page   I then cycle through the reply doing as follows   BufferedReader r   new BufferedReader new InputStreamReader inputStream    String x       x   r readLine    String total        while x   null   total    x  x   r readLine        However this is horrendously slow   Is this inefficient  I m not loading a big web page - www cokezone co uk so the file size is not big  Is there a better way to do this   Thanks  Andy

User · Answer

If the file is long  you can optimize your code by appending to a StringBuilder instead of using a String concatenation for each line

User · Answer

Another possibility with Guava   dependency  compile  com google guava guava 11 0 2   import com google common io ByteStreams       String total   new String ByteStreams toByteArray inputStream

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I am use to read full data      inputStream is one instance InputStream byte   data   new byte inputStream available     inputStream read data   String dataString   new String data

User · Answer

Maybe rather then read  one line at a time  and join the strings  try  read all available  so as to avoid the scanning for end of line  and to also avoid string joins   ie  InputStream available   and InputStream read byte   b   int offset  int length

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byte   buffer   new byte 1024       buffer store for the stream     int bytes     bytes returned from read           Keep listening to the InputStream until an exception occurs     while  true            try                  Read from the InputStream             bytes   mmInStream read buffer                String TOKEN    new String buffer   UTF-8                 String xx   TOKEN  substring 0  bytes

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Possibly somewhat faster than Jaime Soriano s answer  and without the multi-byte encoding problems of Adrian s answer  I suggest   File file   new File   tmp myfile    try       FileInputStream stream   new FileInputStream file        int count      byte   buffer   new byte 1024       ByteArrayOutputStream byteStream           new ByteArrayOutputStream stream available          while  true            count   stream read buffer           if  count  lt   0              break          byteStream write buffer  0  count              String string   byteStream toString        System out format   d bytes     s   n   string length    string     catch  IOException e        e printStackTrace

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Have you tried the built in method to convert a stream to a string  It s part of the Apache Commons library  org apache commons io IOUtils    Then your code would be this one line   String total   IOUtils toString inputStream     The documentation for it can be found here  http   commons apache org io api-1 4 org apache commons io IOUtils html toString 28java io InputStream 29  The Apache Commons IO library can be downloaded from here  http   commons apache org io download io cgi

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The problem in your code is that it s creating lots of heavy String objects  copying their contents and performing operations on them  Instead  you should use StringBuilder to avoid creating new String objects on each append and to avoid copying the char arrays  The implementation for your case would be something like this   BufferedReader r   new BufferedReader new InputStreamReader inputStream    StringBuilder total   new StringBuilder    for  String line   line   r readLine       null          total append line  append   n        You can now use total without converting it to String  but if you need the result as a String  simply add   String result   total toString     I ll try to explain it better      a    b  or a   a   b   where a and b are Strings  copies the contents of both a and b to a new object  note that you are also copying a  which contains the accumulated String   and you are doing those copies on each iteration  a append b   where a is a StringBuilder  directly appends b contents to a  so you don t copy the accumulated string at each iteration

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To convert the InputStream to String we use the          BufferedReader readLine   method  We iterate until the BufferedReader return null which means there s no more data to read  Each line will appended to a StringBuilder and returned as String    public static String convertStreamToString InputStream is             BufferedReader reader   new BufferedReader new InputStreamReader is            StringBuilder sb   new StringBuilder             String line   null          try               while   line   reader readLine       null                    sb append line     n                            catch  IOException e                e printStackTrace              finally               try                   is close                  catch  IOException e                    e printStackTrace                                    return sb toString               And finally from any class where you want to convert call the function  String dataString   Utils convertStreamToString in     complete

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What about this  Seems to give better performance   byte   bytes   new byte 1000    StringBuilder x   new StringBuilder     int numRead   0  while   numRead   is read bytes    gt   0        x append new String bytes  0  numRead        Edit  Actually this sort of encompasses both steelbytes and Maurice Perry s

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Reading one line of text at a time  and appending said line to a string individually is time-consuming both in extracting each line and the overhead of so many method invocations   I was able to get better performance by allocating a decent-sized byte array to hold the stream data  and which is iteratively replaced with a larger array when needed  and trying to read as much as the array could hold   For some reason  Android repeatedly failed to download the entire file when the code used the InputStream returned by HTTPUrlConnection  so I had to resort to using both a BufferedReader and a hand-rolled timeout mechanism to ensure I would either get the whole file or cancel the transfer   private static  final   int         kBufferExpansionSize          32   1024  private static  final   int         kBufferInitialSize            kBufferExpansionSize  private static  final   int         kMillisecondsFactor           1000  private static  final   int         kNetworkActionPeriod          12   kMillisecondsFactor   private String loadContentsOfReader Reader aReader        BufferedReader  br   null      char            array   new char kBufferInitialSize       int             bytesRead      int             totalLength   0      String          resourceContent           long            stopTime      long            nowTime       try               br   new BufferedReader aReader            nowTime   System nanoTime            stopTime   nowTime     long kNetworkActionPeriod   kMillisecondsFactor   kMillisecondsFactor           while   bytesRead   br read array  totalLength  array length - totalLength      -1           amp  amp   nowTime  lt  stopTime                         totalLength    bytesRead              if totalLength    array length                  array   Arrays copyOf array  array length   kBufferExpansionSize               nowTime   System nanoTime                       if bytesRead    -1              resourceContent   new String array  0  totalLength             catch Exception e                e printStackTrace               try               if br    null              br close              catch IOException e                   TODO Auto-generated catch block         e printStackTrace              EDIT  It turns out that if you don t need to have the content re-encoded  ie  you want the content AS IS  you shouldn t use any of the Reader subclasses  Just use the appropriate Stream subclass   Replace the beginning of the preceding method with the corresponding lines of the following to speed it up an extra 2 to 3 times   String  loadContentsFromStream Stream aStream        BufferedInputStream br   null      byte                array      int                 bytesRead      int                 totalLength   0      String              resourceContent      long                stopTime      long                nowTime       resourceContent           try               br   new BufferedInputStream aStream           array   new byte kBufferInitialSize

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I believe this is efficient enough    To get a String from an InputStream  I d call the following method   public static String getStringFromInputStream InputStream stream  throws IOException       int n   0      char   buffer   new char 1024   4       InputStreamReader reader   new InputStreamReader stream   UTF8        StringWriter writer   new StringWriter        while  -1     n   reader read buffer    writer write buffer  0  n       return writer toString        I always use UTF-8  You could  of course  set charset as an argument  besides InputStream

[java] Android Reading from an Input stream efficiently

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