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:
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
byte [] bb = { 10 , 20 , 30 };
ByteBuffer byteBuffer = ByteBuffer.wrap(bb);
Buffer buffer = (Buffer)byteBuffer;
buffer.position( 1 );
System.out.println( "Buffer before flip: "
+ Arrays.toString(( byte [])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
buffer.flip();
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:
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
ByteBuffer byteBuffer = ByteBuffer.allocate( 4 );
byteBuffer.put(( byte ) 20 );
byteBuffer.put(( byte ) 30 );
Buffer buffer = (Buffer)byteBuffer;
buffer.position( 1 );
System.out.println( "Buffer before flip: "
+ Arrays.toString(( byte [])buffer.array())
+ "\nPosition: " + buffer.position()
+ "\nLimit: " + buffer.limit());
buffer.flip();
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–
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