ByteBuffer rewind() methods in Java with Examples

The rewind() method of java.nio.ByteBuffer Class is used to rewind this buffer. The position is set to zero and the mark is discarded. Invoke this method before a sequence of channel-write or get operations, assuming that the limit has already been set appropriately. Invoking this method neither changes nor discards the mark’s value.

Syntax:

public ByteBuffer rewind()

Return Value: This method returns this buffer.

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

Examples 1:

// Java program to demonstrate 
// rewind() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // defining and allocating ByteBuffer 
        // using allocate() method 
        ByteBuffer byteBuffer = ByteBuffer.allocate(4); 
  
        // put byte value in byteBuffer 
        // using put() method 
        byteBuffer.put((byte)20); 
        byteBuffer.put((byte)'a'); 
  
        // print the byte buffer 
        System.out.println("Buffer before operation: "
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition: " + byteBuffer.position() 
                           + "\nLimit: " + byteBuffer.limit()); 
  
        // rewind the Buffer 
        // using rewind() method 
        byteBuffer.rewind(); 
  
        // print the bytebuffer 
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition: " + byteBuffer.position() 
                           + "\nLimit: " + byteBuffer.limit()); 
    } 
} 

Output:

Buffer before operation: [20, 97, 0, 0]
Position: 2
Limit: 4

Buffer after operation: [20, 97, 0, 0]
Position: 0
Limit: 4

Examples 2:

// Java program to demonstrate 
// rewind() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // defining and allocating ByteBuffer 
        // using allocate() method 
        ByteBuffer byteBuffer = ByteBuffer.allocate(5); 
  
        // put byte value in byteBuffer 
        // using put() method 
        byteBuffer.put((byte)20); 
        byteBuffer.put((byte)30); 
        byteBuffer.put((byte)40); 
  
        // mark will be going to discarded by rewind() 
        byteBuffer.mark(); 
  
        // print the buffer 
        System.out.println("Buffer before operation: "
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition: " + byteBuffer.position() 
                           + "\nLimit: " + byteBuffer.limit()); 
  
        // Rewind the Buffer 
        // using rewind() method 
        byteBuffer.rewind(); 
  
        // print the buffer 
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(byteBuffer.array()) 
                           + "\nPosition: " + byteBuffer.position() 
                           + "\nLimit: " + byteBuffer.limit()); 
    } 
} 

Output:

Buffer before operation: [20, 30, 40, 0, 0]
Position: 3
Limit: 5

Buffer after operation: [20, 30, 40, 0, 0]
Position: 0
Limit: 5

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

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