DoubleBuffer rewind() Method in Java with Examples

The rewind() method of java.nio.DoubleBuffer Class is used to rewind this buffer. This method sets the position to zero and the 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. This means that if buffer data is already written then it needs to be copied into another array. For example:

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

Syntax:

public final DoubleBuffer rewind()

Parameters: The method does not take any parameters.



Return Value: This method returns this buffer.

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

Examples 1:

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// Java program to demonstrate
// rewind() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating DoubleBuffer
        // using allocate() method
        DoubleBuffer doubleBuffer = DoubleBuffer.allocate(4);
  
        // put char value in doubleBuffer
        // using put() method
        doubleBuffer.put(10.5);
        doubleBuffer.put(20.5);
  
        // print the double buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
  
        // rewind the Buffer
        // using rewind() method
        doubleBuffer.rewind();
  
        // print the doublebuffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
    }
}

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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:

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// Java program to demonstrate
// rewind() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating DoubleBuffer
        // using allocate() method
        DoubleBuffer doubleBuffer
            = DoubleBuffer.allocate(5);
  
        // put double value in doubleBuffer
        // using put() method
        doubleBuffer.put(10.5);
        doubleBuffer.put(20.5);
        doubleBuffer.put(30.5);
  
        // mark will be going to discarded by rewind()
        doubleBuffer.mark();
  
        // print the buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
  
        // Rewind the Buffer
        // using rewind() method
        doubleBuffer.rewind();
  
        // print the buffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 doubleBuffer.array())
                           + "\nPosition: "
                           + doubleBuffer.position()
                           + "\nLimit: "
                           + doubleBuffer.limit());
    }
}

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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/DoubleBuffer.html#rewind–



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