FloatBuffer rewind() methods in Java with Examples

The rewind() method of java.nio.FloatBuffer Class is used to rewind this buffer. This method sets the position to zero and limit remains unaffected and if there is any position which was previously marked, will be discarded. This method should be invoked when there is any necessity of sequence of channel-write or get operations. It means that if buffer data is already written then it is needed to be copied into another array. For example:

 
out.write(buf);   // Writes the remaining data
buf.rewind();     // Rewind the buffer
buf.get(array);   // Copy data into array

Syntax:

public final FloatBuffer rewind()

Parameters: The method does not take any parameters.

Return Value: The 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 FloatBuffer
        // using allocate() method
        FloatBuffer floatBuffer = FloatBuffer.allocate(4);

        // put char value in FloatBuffer
        // using put() method
        floatBuffer.put(10.5f);
        floatBuffer.put(20.5f);

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

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

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

Output:

Buffer before operation: [10.5, 20.5, 0.0, 0.0]
Position: 2
Limit: 4

Buffer after operation: [10.5, 20.5, 0.0, 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 FloatBuffer
        // using allocate() method
        FloatBuffer floatBuffer
            = FloatBuffer.allocate(5);

        // put float value in floatBuffer
        // using put() method
        floatBuffer.put(10.5f);
        floatBuffer.put(20.5f);
        floatBuffer.put(30.5f);

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

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

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

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

Output:

Buffer before operation: [10.5, 20.5, 30.5, 0.0, 0.0]
Position: 3
Limit: 5

Buffer after operation: [10.5, 20.5, 30.5, 0.0, 0.0]
Position: 0
Limit: 5

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