Buffer mark() methods in Java with Examples

The mark() method of java.nio.Buffer Class is used to set this buffer’s mark at its position.
Syntax:

public Buffer mark()

Return Value: This method returns this buffer.
Below are the examples to illustrate the mark() method:
Examples 1:

Java

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

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

public class GFG {

    public static void main(String[] args)
    {

        try {

            byte[] barr = { 10, 20, 30, 40 };

            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.wrap(barr);

            // Typecasting ByteBuffer into Buffer
            Buffer bb1 = (Buffer)bb;

            // try to set the position at index 2
            bb1.position(2);

            // Set this buffer mark position
            // using mark() method
            bb1.mark();

            // try to set the position at index 4
            bb1.position(4);

            // display position
            System.out.println("position before reset: "
                               + bb1.position());

            // try to call reset() to restore
            // to the position we marked
            bb1.reset();

            // display position
            System.out.println("position after reset: "
                               + bb1.position());
        }

        catch (InvalidMarkException e) {
            System.out.println("new position is less than "
                               + "the position we marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

Output:

position before reset: 4
position after reset: 2

Examples 2: To demonstrate InvalidMarkException

Java

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

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

public class GFG {

    public static void main(String[] args)
    {

        try {

            byte[] barr = { 10, 20, 30, 40 };

            // creating object of ByteBuffer
            // and allocating size capacity
            ByteBuffer bb = ByteBuffer.wrap(barr);

            // Typecasting ByteBuffer into Buffer
            Buffer bb1 = (Buffer)bb;

            // try to set the position at index 2
            bb1.position(2);

            // Set this buffer mark position
            // using mark() method
            bb1.mark();

            // try to set the position at index 4
            bb1.position(1);

            // display position
            System.out.println("position before reset: "
                               + bb1.position());

            // try to call reset() to restore
            // to the position we marked
            bb1.reset();

            // display position
            System.out.println("position after reset: "
                               + bb1.position());
        }

        catch (InvalidMarkException e) {
            System.out.println("\new position is less than "
                               + "the position we marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

Output:

position before reset: 1

new position is less than the position we marked before 
Exception throws: java.nio.InvalidMarkException

Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#mark–