CharBuffer rewind() methods in Java with Examples

The rewind() method of java.nio.CharBuffer 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 CharBuffer
        // using allocate() method
        CharBuffer charBuffer = CharBuffer.allocate(4);

        // put char value in charBuffer
        // using put() method
        charBuffer.put('a');
        charBuffer.put((char)105);

        // print the char buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());

        // rewind the Buffer
        // using rewind() method
        charBuffer.rewind();

        // print the charbuffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
    }
}

Output:

Buffer before operation: [a, i,,  ]
Position: 2
Limit: 4

Buffer after operation: [a, i,,  ]
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 CharBuffer
        // using allocate() method
        CharBuffer charBuffer
            = CharBuffer.allocate(5);

        // put byte value in charBuffer
        // using put() method
        charBuffer.put('a');
        charBuffer.put('b');
        charBuffer.put('c');

        // mark will be going to discarded by rewind()
        charBuffer.mark();

        // print the buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());

        // Rewind the Buffer
        // using rewind() method
        charBuffer.rewind();

        // print the buffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
    }
}

Output:

Buffer before operation: [a, b, c,,  ]
Position: 3
Limit: 5

Buffer after operation: [a, b, c,,  ]
Position: 0
Limit: 5

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