IntBuffer compact() method in Java

Last Updated : 20 Sep, 2018
The compact() method of java.nio.IntBuffer Class is used to compact the given buffer. The values between the buffer's current position and its limit are copied to the beginning of the buffer. The buffer's position is then set to n+1 and its limit is set to its capacity. The buffer's position is set to the number of floats copied. Syntax: 
public abstract IntBuffer compact()
Return Value: This method returns the new IntBuffer with the same content as that of this buffer. Exception: This method throws the ReadOnlyBufferException, If this buffer is read-only. Below program illustrates the compact() method: Examples 1: Java 
// Java program to demonstrate
// compact() method

import java.nio.*;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // Declaring the capacity of the IntBuffer
        int capacity = 10;

        // Creating the IntBuffer

        // creating object of Intbuffer
        // and allocating size capacity
        IntBuffer ib = IntBuffer.allocate(capacity);

        // putting the value in Intbuffer
        ib.put(8);
        ib.put(9);
        ib.put(9);

        // print the IntBuffer
        System.out.println("Original IntBuffer: "
                           + Arrays.toString(ib.array()));

        System.out.println("Position: " + ib.position());

        System.out.println("limit: " + ib.limit());

        // Creating a compacted  IntBuffer of same IntBuffer
        // using compact() method
        IntBuffer IntBuffer = ib.compact();

        // print the IntBuffer
        System.out.println("\nCompacted IntBuffer: "
                           + Arrays.toString(IntBuffer.array()));

        System.out.println("Position: " + IntBuffer.position());

        System.out.println("limit: " + IntBuffer.limit());

        // putting the value in compacted Intbuffer
        IntBuffer.put(9);

        // print the IntBuffer
        System.out.println("\nUpdated Compacted IntBuffer: "
                           + Arrays.toString(IntBuffer.array()));
        System.out.println("Position: " + IntBuffer.position());
        System.out.println("limit: " + IntBuffer.limit());
    }
}
Output: 
Original IntBuffer: [8, 9, 9, 0, 0, 0, 0, 0, 0, 0]
Position: 3
limit: 10

Compacted IntBuffer: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Position: 7
limit: 10

Updated Compacted IntBuffer: [0, 0, 0, 0, 0, 0, 0, 9, 0, 0]
Position: 8
limit: 10
Examples 2: To demonstrate ReadOnlyBufferException Java 
// Java program to demonstrate
// compact() method

import java.nio.*;
import java.util.*;

public class GFG {
    public static void main(String[] args)
    {

        // Declaring the capacity of the IntBuffer
        int capacity = 10;

        // Creating the IntBuffer
        try {

            // creating object of IntBuffer
            // and allocating size capacity
            IntBuffer ib = IntBuffer.allocate(capacity);

            // putting the value in Intbuffer
            ib.put(8);
            ib.put(9);
            ib.put(9);
            ib.rewind();

            // Creating a read-only copy of IntBuffer
            // using asReadOnlyBuffer() method
            IntBuffer ib1 = ib.asReadOnlyBuffer();

            // print the ReadOnlyBuffer
            System.out.print("ReadOnlyBuffer IntBuffer: ");

            while (ib1.hasRemaining())
                System.out.print(ib1.get() + ", ");
            System.out.println("");

            // print the Position of IntBuffer ib
            System.out.println("\nPosition: " + ib.position());

            // print the Limit of IntBuffer ib
            System.out.println("\nlimit: " + ib.limit());

            // Creating a compacted  IntBuffer of same ReadOnlyBuffer
            // using compact() method
            System.out.println("\nTrying to compact the ReadOnlyBuffer ib1");

            IntBuffer IntBuffer = ib1.compact();
        }

        catch (IllegalArgumentException e) {
            System.out.println("Exception throws " + e);
        }

        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws " + e);
        }
    }
}
Output: 
ReadOnlyBuffer IntBuffer: 8, 9, 9, 0, 0, 0, 0, 0, 0, 0, 

Position: 0

limit: 10

Trying to compact the ReadOnlyBuffer ib1
Exception throws java.nio.ReadOnlyBufferException
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