Buffer flip() methods in Java with Examples

Last Updated : 18 Jul, 2019

The flip() method of java.nio.ByteBuffer Class is used to flip this buffer. The limit is set to the current position and then the position is set to zero. If the mark is defined then it is discarded. After a sequence of channel-read or put operations, invoke this method to prepare for a sequence of channel-write or relative get operations.

For example:

  buf.put(magic);    // Prepend header  in.read(buf);      // Read data into rest of buffer  buf.flip();        // Flip buffer  out.write(buf);    // Write header + data to channel

This method is often used in conjunction with the compact() method when transferring data from one place to another.

Syntax:

public Buffer flip()

Return Value: This method returns this buffer.

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

Examples 1:

   // Java program to demonstrate 
// flip() method 
  
import java.nio.*; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
  
        // Declare and initialize the byte array 
        byte[] bb = { 10, 20, 30 }; 
  
        // wrap the byte array into ByteBuffer 
        // using wrap() method 
        ByteBuffer byteBuffer = ByteBuffer.wrap(bb); 
  
        // Typecast ByteBuffer to Buffer 
        Buffer buffer = (Buffer)byteBuffer; 
  
        // set position at index 1 
        buffer.position(1); 
  
        // print the buffer 
        System.out.println("Buffer before flip: "
                           + Arrays.toString((byte[])buffer.array()) 
                           + "\nPosition: " + buffer.position() 
                           + "\nLimit: " + buffer.limit()); 
  
        // Flip the Buffer 
        // using flip() method 
        buffer.flip(); 
  
        // print the buffer 
        System.out.println("\nBuffer after flip: "
                           + Arrays.toString((byte[])buffer.array()) 
                           + "\nPosition: " + buffer.position() 
                           + "\nLimit: " + buffer.limit()); 
    } 
} 
 
  

Output:

  Buffer before flip: [10, 20, 30]  Position: 1  Limit: 3    Buffer after flip: [10, 20, 30]  Position: 0  Limit: 1

Examples 2:

   // Java program to demonstrate 
// flip() 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)30); 
  
        // Typecast ByteBuffer to Buffer 
        Buffer buffer = (Buffer)byteBuffer; 
  
        // set position at index 1 
        buffer.position(1); 
  
        // print the buffer 
        System.out.println("Buffer before flip: "
                           + Arrays.toString((byte[])buffer.array()) 
                           + "\nPosition: " + buffer.position() 
                           + "\nLimit: " + buffer.limit()); 
  
        // Flip the Buffer 
        // using flip() method 
        buffer.flip(); 
  
        // print the buffer 
        System.out.println("\nBuffer after flip: "
                           + Arrays.toString((byte[])buffer.array()) 
                           + "\nPosition: " + buffer.position() 
                           + "\nLimit: " + buffer.limit()); 
    } 
} 
 
  

Output:

  Buffer before flip: [20, 30, 0, 0]  Position: 1  Limit: 4    Buffer after flip: [20, 30, 0, 0]  Position: 0  Limit: 1

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

ByteBuffer flip() methods in Java with Examples

RohitPrasad3

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Buffer flip() methods in Java with Examples

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