ByteBuffer duplicate() method in Java with Examples

The duplicate() method of java.nio.ByteBuffer class is used to create a new byte buffer that shares this buffer’s content.

The content of the new buffer will be that of this buffer. Changes to this buffer’s content will be visible in the new buffer, and vice versa; the two buffers’ position, limit, and mark values will be independent.

The new buffer’s capacity, limit, position, and mark values will be identical to those of this buffer. The new buffer will be direct if, and only if, this buffer is direct, and it will be read-only if, and only if, this buffer is read-only.

Syntax :

public abstract ByteBuffer duplicate()

Return Value: This method returns the new byte buffer which is carrying the previous byte buffer content.

Below are the examples to illustrate the duplicate() method:

Examples 1: Using direct ByteBuffer

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// Java program to demonstrate
// duplicate() method
// Using direct ByteBuffer
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the ByteBuffer
        int capacity = 4;
  
        // Creating the ByteBuffer
        try {
  
            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb1 = ByteBuffer.allocate(capacity);
  
            // putting the int to byte typecast value value in ByteBuffer
            bb1.put((byte)20);
            bb1.put((byte)30);
            bb1.put((byte)40);
            bb1.put((byte)50);
            bb1.rewind();
  
            // print the Original ByteBuffer
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb1.array()));
  
            // Creating a duplicate copy of ByteBuffer
            // using duplicate() method
            ByteBuffer bb2 = bb1.duplicate();
  
            // print the duplicate copy of ByteBuffer
            System.out.print("\nDuplicate ByteBuffer: "
                             + Arrays.toString(bb2.array()));
        }
  
        catch (IllegalArgumentException e) {
  
            System.out.println("Exception thrown : " + e);
        }
  
        catch (ReadOnlyBufferException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:

Original ByteBuffer:  [20, 30, 40, 50]

Duplicate ByteBuffer: [20, 30, 40, 50]

Examples 2: Using read-only ByteBuffer

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// Java program to demonstrate
// duplicate() method
// using read-only ByteBuffer
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the ByteBuffer
        int capacity = 4;
  
        // Creating the ByteBuffer
        try {
  
            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb1 = ByteBuffer.allocate(capacity);
  
            // putting the int to byte typecast value in ByteBuffer
            bb1.put((byte)20);
            bb1.put((byte)30);
            bb1.put((byte)40);
            bb1.put((byte)50);
            bb1.rewind();
  
            // print the Original ByteBuffer
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb1.array()));
  
            // Creating a read-only copy of ByteBuffer
            // using asReadOnlyBuffer() method
            ByteBuffer readonly = bb1.asReadOnlyBuffer();
  
            // print the read-only copy of of ByteBuffer
            System.out.print("\nRead-only ByteBuffer:  ");
            while (readonly.hasRemaining())
                System.out.print(readonly.get() + ", ");
            System.out.println("");
  
            // Rewinding the readonly ByteBuffer
            readonly.rewind();
  
            // Creating a duplicate copy of ByteBuffer
            // using duplicate() method
            ByteBuffer bb2 = readonly.duplicate();
  
            // print the duplicate copy of of ByteBuffer
            System.out.print("\nDuplicate copy of read-only ByteBuffer:  ");
  
            while (bb2.hasRemaining())
                System.out.print(bb2.get() + ", ");
            System.out.println("");
        }
  
        catch (IllegalArgumentException e) {
  
            System.out.println("Exception thrown : " + e);
        }
  
        catch (ReadOnlyBufferException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

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Output:

Original ByteBuffer:  [20, 30, 40, 50]

Read-only ByteBuffer:  20, 30, 40, 50, 

Duplicate copy of read-only ByteBuffer:  20, 30, 40, 50,


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