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Buffer mark() methods in Java with Examples
  • Last Updated : 18 Jul, 2019

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 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 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("\nnew 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–

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