ByteBuffer arrayOffset() method in Java with Examples - GeeksforGeeks

20 Sep, 2018
The arrayOffset() method of java.nio.ByteBuffer class is used to return the offset within the given buffer’s backing array of the first element of the buffer.
If this buffer is backed by an array then buffer position p corresponds to array index p + arrayOffset().
Invoke the hasArray method before invoking this method in order to ensure that this buffer has an accessible backing array.
Syntax :
public final int arrayOffset()
Return Value: This method returns the offset within this buffer’s array of the first element of the buffer
Exception:: This method throws the ReadOnlyBufferException, If this buffer is backed by an array but is read-only.
Below are the examples to illustrate the arrayOffset() method:
Example 1:
// Java program to demonstrate// arrayOffset() method  import java.nio.*;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Declaring the capacity of the ByteBuffer        int capacity = 4;          // Creating the ByteBuffer        try {              // creating object of ByteBuffer            // and allocating size capacity            ByteBuffer bb = ByteBuffer.allocate(capacity);              // putting the int to byte typecast value in ByteBuffer            bb.put((byte)20);            bb.put((byte)30);            bb.put((byte)40);            bb.put((byte)50);            bb.rewind();              // print the ByteBuffer            System.out.println("ByteBuffer: "                               + Arrays.toString(bb.array()));              // print the arrayOffset            System.out.println("arrayOffset: "                               + bb.arrayOffset());        }          catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }          catch (ReadOnlyBufferException e) {            System.out.println("Exception throws" + e);        }    }}
ByteBuffer: [20, 30, 40, 50]
arrayOffset: 0

Example 2:
// Java program to demonstrate// arrayOffset() method  import java.nio.*;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Declaring the capacity of the  ByteBuffer        int capacity = 3;          // Creating the  ByteBuffer        try {              // creating object of  ByteBuffer            // and allocating size capacity            ByteBuffer bb = ByteBuffer.allocate(capacity);              // putting the value in  ByteBuffer            bb.put((byte)20);            bb.put((byte)30);            bb.put((byte)40);            bb.rewind();              // Creating a read-only copy of  ByteBuffer            // using asReadOnlyBuffer() method            ByteBuffer bb1 = bb.asReadOnlyBuffer();              // print the  ByteBuffer            System.out.print("Read only buffer : ");            while (bb1.hasRemaining())                System.out.print(bb1.get() + ", ");              // next line            System.out.println("");              // print the arrayOffset            System.out.println("\nTry to print the array offset"                               + " of read only buffer");            System.out.println("arrayOffset: " + bb1.arrayOffset());        }          catch (IllegalArgumentException e) {            System.out.println("Exception throws: " + e);        }          catch (ReadOnlyBufferException e) {            System.out.println("Exception throws: " + e);        }    }}
Read only buffer : 20, 30, 40, 

Try to print the array offset of read only buffer
Exception throws: java.nio.ReadOnlyBufferException

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