ByteBuffer array() method in Java with Examples

The array() method of java.nio.ByteBuffer class is used to return the byte array that backs the taken buffer.
Modifications to this buffer’s content will cause the returned array’s content to be modified, and vice versa.
Invoke the hasArray() method before invoking this method in order to ensure that this buffer has an accessible backing array.

Syntax :

public final byte[] array()

Return Value: This method returns the array that backs this buffer.
Exception: This method throws the ReadOnlyBufferException, If this buffer is backed by an array but is read-only.

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

Example 1:

Java

// Java program to demonstrate
// array() method

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 bb = ByteBuffer.allocate(capacity);

            // putting the int to byte typecast value in ByteBuffer
            bb.put((byte)20);
            bb.put((byte)30);
            bb.put((byte)40);
            bb.put((byte)50);

            // print the ByteBuffer
            System.out.println("ByteBuffer:  "
                               + Arrays.toString(bb.array()));

            // getting byte array from ByteBuffer
            // using array() method
            byte[] arr = bb.array();

            // print the byte array
            System.out.println("\nbyte array: " +
                                    Arrays.toString(arr));
        }

        catch (IllegalArgumentException e) {

            System.out.println("Exception throws: " + e);
        }
    }
}

Output:

ByteBuffer:  [20, 30, 40, 50]

byte array: [20, 30, 40, 50]

Example 2:

Java

// Java program to demonstrate
// array() method

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 bb = ByteBuffer.allocate(capacity);

            // putting the int to byte typecast value
            // in ByteBuffer
            bb.put((byte)20);
            bb.put((byte)30);
            bb.put((byte)40);
            bb.put((byte)50);
            bb.rewind();

            // print the ByteBuffer
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb.array()));

            // Creating a read-only copy of ByteBuffer
            // using asReadOnlyBuffer() method
            ByteBuffer bb1 = bb.asReadOnlyBuffer();
            bb1.rewind();

            // print the ByteBuffer
            System.out.print("\nReadOnlyBuffer ByteBuffer : ");

            while (bb1.hasRemaining())
                System.out.print(bb1.get() + ", ");

            // getting byte array from read-only
            // ByteBuffer using array() method
            System.out.println("\n\nTrying to get the array"
                               + " from bb1 for editing");
            byte[] arr = bb1.array();
        }

        catch (IllegalArgumentException e) {

            System.out.println("Exception throws: " + e);
        }

        catch (ReadOnlyBufferException e) {

            System.out.println("Exception throws: " + e);
        }
    }
}

Output:

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

ReadOnlyBuffer ByteBuffer : 20, 30, 40, 50, 

Trying to get the array from bb1 for editing
Exception throws: java.nio.ReadOnlyBufferException