CharBuffer arrayOffset() method in Java

The arrayOffset() method of java.nio.CharBuffer class is used to return the offset within the buffer’s backing array of the first element of the buffer. It means that if this buffer is backed by an array, then buffer position p corresponds to array index p + arrayOffset().

Inorder to check whether this buffer has a backing array, hasArray() method can be used. It ensures that this buffer has an accessible backing array.

Syntax:

public final int arrayOffset()

Return Value: This method returns the offset within this buffer’s array of the first element of the buffer.

Exception: This method throws ReadOnlyBufferException if this buffer is backed by an array but is read-only

Below program illustrates the arrayOffset() method.

Example 1:

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

import java.nio.*;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // Declaring the capacity of the CharBuffer
        int capacity = 10;

        // Creating the CharBuffer
        try {

            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer cb = CharBuffer.allocate(capacity);

            // putting the value in CharBuffer
            cb.put('a');
            cb.put(2, 'b');

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

            // print the arrayOffset
            System.out.println("arrayOffset: "
                               + cb.arrayOffset());
        }

        catch (IllegalArgumentException e) {
            System.out.println("IllegalArgumentException catched");
        }

        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws" + e);
        }
    }
}

Output:

CharBuffer: [a, , b, , , , , , , ]
arrayOffset: 0

Example 2: To demonstrate ReadOnlyBufferException

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

import java.nio.*;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // Declaring the capacity of the CharBuffer
        int capacity = 10;

        // Creating the CharBuffer
        try {

            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer fb = CharBuffer.allocate(capacity);

            // putting the value in CharBuffer
            fb.put('a');
            fb.put(2, 'b');
            fb.rewind();

            // Creating a read-only copy of CharBuffer
            // using asReadOnlyBuffer() method
            CharBuffer cb1 = fb.asReadOnlyBuffer();

            // print the CharBuffer
            System.out.print("Read only buffer : ");
            while (cb1.hasRemaining())
                System.out.print(cb1.get() + ", ");

            // next line
            System.out.println("");

            // print the arrayOffset
            System.out.println("\nTry to print the array offset"
                               + " of read only buffer");
            System.out.println("arrayOffset: " + cb1.arrayOffset());
        }

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

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

Output:

Read only buffer : a, , b, , , , , , , , 

Try to print the array offset of read only buffer
Exception throws: java.nio.ReadOnlyBufferException