NIO: Reading and writing to Multiple Buffers

Step 1: Create buffers.

ByteBuffer buffer1 = ByteBuffer.allocate(1024);

ByteBuffer buffer2 = ByteBuffer.allocate(1024);

ByteBuffer buffer3 = ByteBuffer.allocate(1024);

Step 2: Write some content to the buffers.

buffer1.put(new String("content from file1\n").getBytes());

buffer2.put(new String("content from file2\n").getBytes());

buffer3.put(new String("content from file3\n").getBytes());

Step 3: Flip the buffers..

buffer1.flip();

buffer2.flip();

buffer3.flip();

Step 4: Create ByteBuffer array and write the buffer array to channel.

ByteBuffer[] buffers = {buffer1, buffer2, buffer3};

FileChannel channel = FileChannel.open(Paths.get(FILE_PATH), CREATE, WRITE);

channel.write(buffers);

Test.java

package com.sample.app;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import static java.nio.file.StandardOpenOption.CREATE;
import static java.nio.file.StandardOpenOption.WRITE;


public class Test {

 private static final String FILE_PATH = "/Users/krishna/Documents/demo.txt";

 public static void main(String... args) throws IOException {
  ByteBuffer buffer1 = ByteBuffer.allocate(1024);
  ByteBuffer buffer2 = ByteBuffer.allocate(1024);
  ByteBuffer buffer3 = ByteBuffer.allocate(1024);
  
  buffer1.put(new String("content from file1\n").getBytes());
  buffer2.put(new String("content from file2\n").getBytes());
  buffer3.put(new String("content from file3\n").getBytes());
  
  buffer1.flip();
  buffer2.flip();
  buffer3.flip();
  
  ByteBuffer[] buffers = {buffer1, buffer2, buffer3};
  
  FileChannel channel = FileChannel.open(Paths.get(FILE_PATH), CREATE, WRITE);
  channel.write(buffers);
  
  channel.close();
  
 }
}

Run Test.java and open demo.txt you can see below content.

$cat demo.txt

content from file1

content from file2

content from file3

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