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java.nio.Buffer Class in Java

  • Last Updated : 13 May, 2021

The Buffer class provides a buffer or a container for data chunks of specific primitive types. A finite sequence of elements is stored linearly in a buffer.

Important properties of a buffer that make it convenient to perform read and write operations in the data are:

  • Capacity: This property determines the maximum number of elements that can be there in a buffer.
  • Limit: This property determines the limit of the data that can be read or write by providing the index of the elements.
  • Position: This property determines the location of the current element in the buffer.

Syntax: Class declaration

public abstract class Buffer extends Object

Buffer class provides a subclass for each of the following buffer data types such as ByteBuffer, MappedByteBuffer, CharBuffer, DoubleBuffer, FloatBuffer, IntBuffer, LongBuffer, ShortBuffer. Buffer class inherits the following methods from class java.lang.Object such as clone(), finalize(), getClass(), hashCode(), notify(), notifyAll(), toString(), wait(). Now, moving on to the methods of Buffer class is as follows as shown alphabetically in the tabular format shown below:

MethodDescription
array()This method returns the array that backs this buffer
arrayOffset()This method returns the offset within this buffer’s backing array of the first element of the buffer 
capacity()This method returns this buffer’s capacity.
clear()This method clears this buffer.
flip()This method flips this buffer.
hasArray()This method tells whether or not this buffer is backed by an accessible array.
hasRemaining()This method tells whether there are any elements between the current position and the limit.
isDirect()This method tells whether or not this buffer is direct.
isReadOnly()This method tells whether or not this buffer is read-only.
limit()This method returns this buffer’s limit.
limit(int newLimit)This method sets this buffer’s limit.
mark()This method sets this buffer’s mark at its position.
position()This method returns this buffer’s position.
position(int newPosition)This method sets this buffer’s position.
remaining()This method returns the number of elements between the current position and the limit.
reset()This method resets this buffer’s position to the previously marked position.
rewind()This method rewinds this buffer.

Implementation: Buffer class and its methods



Example 1

Java




// Java program to demonstrate Buffer Class
 
// Importing required libraries
import java.nio.*;
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Declaring the capacity of the ByteBuffer
        int capacity = 5;
 
        // Try block to check for exceptions
        try {
 
            // Creating the ByteBuffer
 
            // Creating object of ByteBuffer class and
            // allocating size capacity
            ByteBuffer bufferObj
                = ByteBuffer.allocate(capacity);
 
            // Putting the int to byte typecast
            // value in ByteBuffer using put() method
 
            // Custom input entries
            bufferObj.put((byte)10);
            bufferObj.put((byte)20);
            bufferObj.put((byte)30);
            bufferObj.put((byte)40);
            bufferObj.put((byte)50);
 
            // Typecasting ByteBuffer into Buffer
            Buffer bufferObj1 = (Buffer)bufferObj;
 
            // Getting array that backs this buffer
            // using array() method
            byte[] arr = (byte[])bufferObj1.array();
 
            // Display message only
            System.out.print(" The array is : [");
 
            // Print the array
            for (int i = 0; i < arr.length; i++)
                System.out.print(" " + arr[i]);
            System.out.print(" ]");
        }
 
        // Catch block to handle the exception
        catch (ReadOnlyBufferException e) {
 
            // Print message where exception occured
            // is displayed on console
            System.out.println("Exception throws: " + e);
        }
    }
}
Output
 The array is : [ 10 20 30 40 50 ]

Example 2

Java




// Java program to demonstrate Buffer class
 
// Importing required libraries
import java.nio.*;
import java.util.*;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
 
        // try block to check for exceptions
        try {
 
            // Creating and initializing byte array
            // with custom elements
            byte[] barr = { 10, 20, 30, 40, 50 };
 
            // Creating object of ByteBuffer class
            // and allocating size capacity
            ByteBuffer bufferObj = ByteBuffer.wrap(barr);
 
            // Typecasting ByteBuffer into Buffer
            Buffer bufferObj1 = (Buffer)bufferObj;
 
            // now trying to set the position at index 2
            bufferObj1.position(2);
 
            // Setting this buffer mark position
            // using mark() method
            bufferObj1.mark();
 
            // Again trying to set the position at index 4
            bufferObj1.position(5);
 
            // Display the position
            System.out.println("position before reset: "
                               + bufferObj1.position());
 
            // Now trying to call clear() to restore
            // to the position at index 0 by discarding the
            // mark
            bufferObj1.clear();
 
            // Print aand display the position
            System.out.println("position after reset: "
                               + bufferObj1.position());
        }
 
        // Catch block to handle the exception
        catch (InvalidMarkException e) {
 
            // Display message to be showcase when exception
            // occured
            System.out.println(
                "new position is less than "
                + "the position we marked before ");
 
            // Print the exception on the console
            // along with display message
            System.out.println("Exception throws: " + e);
        }
    }
}
Output
position before reset: 5
position after reset: 0

 

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