Elegant way to read file into byte array in Java

Question

Possible Duplicate    File to byte   in Java       I want to read data from file and unmarshal it to Parcel  In documentation it is not clear  that FileInputStream has method to read all its content  To implement this  I do folowing   FileInputStream filein   context openFileInput FILENAME     int read   0  int offset   0  int chunk size   1024  int total size   0   ArrayList lt byte   gt  chunks   new ArrayList lt byte   gt     chunks add new byte chunk size      first I read data from file chunk by chunk while    read   filein read chunks get chunks size  -1   offset  buffer size      -1        total size  read      if  read    buffer size             chunks add new byte buffer size            int index   0      then I create big buffer         byte   rawdata   new byte total size       then I copy data from every chunk in this buffer for  byte    chunk  chunks        for  byte bt   chunk             index    0           rawdata index    bt           if  index  gt   total size  break            if  index gt   total size  break        and clear chunks array chunks clear        finally I can unmarshall this data to Parcel Parcel parcel   Parcel obtain    parcel unmarshall rawdata 0 rawdata length     I think this code looks ugly  and my question is  How to do read data from file into byte   beautifully

User · Answer

Use a ByteArrayOutputStream  Here is the process    Get an InputStream to read data Create a ByteArrayOutputStream  Copy all the InputStream into the OutputStream Get your byte   from the ByteArrayOutputStream using the toByteArray   method

User · Answer

This works for me   File file        byte   data   new byte  int  file length     try       new FileInputStream file  read data     catch  Exception e        e printStackTrace

User · Answer

This will also work   import java io     public class IOUtil        public static byte   readFile String file  throws IOException           return readFile new File file               public static byte   readFile File file  throws IOException              Open file         RandomAccessFile f   new RandomAccessFile file   r            try                  Get and check length             long longlength   f length                int length    int  longlength              if  length    longlength                  throw new IOException  File size  gt   2 GB                   Read file and return data             byte   data   new byte length               f readFully data               return data            finally               f close

User · Answer

Have a look at the following apache commons function   org apache commons io FileUtils readFileToByteArray File

User · Answer

A long time ago   Call any of these  byte   org apache commons io FileUtils readFileToByteArray File file  byte   org apache commons io IOUtils toByteArray InputStream input     From  http   commons apache org io   If the library footprint is too big for your Android app  you can just use relevant classes from the commons-io library  Today  Java 7  or Android API Level 26    Luckily  we now have a couple of convenience methods in the nio packages  For instance   byte   java nio file Files readAllBytes Path path    Javadoc here

User · Answer

If you use Google Guava  and if you don t  you should   you can call  ByteStreams toByteArray InputStream  or Files toByteArray File

[java] Elegant way to read file into byte[] array in Java

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