Friday 7 June 2019

Java: Convert InputStream to ByteArray


Approach 1: Read entire input stream to ByteArrayOutputStream.
public static byte[] getByteArray(InputStream inputStream) throws IOException {
         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

         int nRead;
         byte[] data = new byte[16384];

         try {
                  while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
                           byteArrayOutputStream.write(data, 0, nRead);
                  }
         } catch (IOException e) {
                  e.printStackTrace();
                  if (inputStream != null) {
                           inputStream.close();
                  }
         }

         return byteArrayOutputStream.toByteArray();
}

App.java
package com.sample.app;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

public class App {

 public static byte[] getByteArray(InputStream inputStream) throws IOException {
  ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

  int nRead;
  byte[] data = new byte[16384];

  try {
   while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
    byteArrayOutputStream.write(data, 0, nRead);
   }
  } catch (IOException e) {
   e.printStackTrace();
   if (inputStream != null) {
    inputStream.close();
   }
  }

  return byteArrayOutputStream.toByteArray();
 }

 public static void main(String args[]) throws IOException {
  FileInputStream fis = new FileInputStream(new File("/Users/krishna/Desktop/TODO.txt"));
  byte[] data = getByteArray(fis);
  
  System.out.println(new String(data));
 }
}

Approach 2: From Java9 onwards, inputstream class provides ‘readAllBytes’ method to get byte array from input stream.
public byte[] readAllBytes()
public int readNBytes(byte[] b, int off, int len)

Approach 3: Using DataInputStream.
byte[] bytes = new byte[(int) file.length()];

try (DataInputStream dataInputStream = new DataInputStream(new FileInputStream(file));) {
         dataInputStream.readFully(bytes);
         return bytes;
}


App.java
package com.sample.app;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class App {

 public static byte[] getByteArray(File file) throws IOException {

  byte[] bytes = new byte[(int) file.length()];
  
  try (DataInputStream dataInputStream = new DataInputStream(new FileInputStream(file));) {
   dataInputStream.readFully(bytes);
   return bytes;
  }

 }

 public static void main(String args[]) throws IOException {
  byte[] data = getByteArray(new File("/Users/krishna/Desktop/TODO.txt"));

  System.out.println(new String(data));
 }
}


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