ByteBuffer compact() method in Java

The buffer can be compacted using the compact() method in the class java.nio.ByteBuffer. This method does not require a parameter and it returns the new compacted ByteBuffer with the same content as the original buffer. If the buffer is read-only, then the ReadOnlyBufferException is thrown.

A program that demonstrates this is given as follows −

Example

 Live Demo

import java.nio.*;
import java.util.*;
public class Demo {
   public static void main(String[] args) {
      int n = 5;
      try {
         ByteBuffer buffer = ByteBuffer.allocate(n);
         buffer.put((byte)5);
         buffer.put((byte)8);
         buffer.put((byte)3);
         System.out.println("The Original ByteBuffer is: " + Arrays.toString(buffer.array()));
         System.out.println("The position is: " + buffer.position());
         System.out.println("The limit is: " + buffer.limit());
         ByteBuffer bufferCompact = buffer.compact();
         System.out.println("
The Compacted ByteBuffer is: " + Arrays.toString(bufferCompact.array()));
         System.out.println("The position is: " + bufferCompact.position());
         System.out.println("The limit is: " + bufferCompact.limit());
      } catch (IllegalArgumentException e) {
         System.out.println("Error!!! IllegalArgumentException");
      } catch (ReadOnlyBufferException e) {
         System.out.println("Error!!! ReadOnlyBufferException");
      }
   }
}

Output

The Original ByteBuffer is: [5, 8, 3, 0, 0]
The position is: 3
The limit is: 5
The Compacted ByteBuffer is: [0, 0, 3, 0, 0]
The position is: 2
The limit is: 5