Buffer arrayOffset() method in Java with Examples
Last Updated :
28 Jun, 2019
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The arrayOffset() method of java.nio.Buffer 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:
Java
Java
public abstract 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);
// Typecasting ByteBuffer into Buffer
Buffer buffer = (Buffer)bb;
// offset within this buffer's array
// of the first element of the buffer
// using arrayOffset() method
int offset = buffer.arrayOffset();
// print the array
System.out.println("arrayOffset is : "
+ offset);
}
catch (ReadOnlyBufferException e) {
System.out.println("buffer is backed by an "
+ "array but is read-only");
System.out.println("Exception throws: " + e);
}
}
}
// Java program to demonstrate// arrayOffset() methodimport 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); // Typecasting ByteBuffer into Buffer Buffer buffer = (Buffer)bb; // offset within this buffer's array // of the first element of the buffer // using arrayOffset() method int offset = buffer.arrayOffset(); // print the array System.out.println("arrayOffset is : " + offset); } catch (ReadOnlyBufferException e) { System.out.println("buffer is backed by an " + "array but is read-only"); System.out.println("Exception throws: " + e); } }}
Output:
Example 2: For ReadOnlyBufferException
arrayOffset is : 0
// 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);
// Creating a read-only copy of ByteBuffer
// using asReadOnlyBuffer() method
ByteBuffer bb1 = bb.asReadOnlyBuffer();
// Typecasting read-only ByteBuffer
// into read-only Buffer
Buffer buffer = (Buffer)bb1;
// offset within this buffer's array
// of the first element of the buffer
// using arrayOffset() method
int offset = buffer.arrayOffset();
// print the array
System.out.println("arrayOffset is : "
+ offset);
}
catch (ReadOnlyBufferException e) {
System.out.println("buffer is backed by "
+ "an array but is read-only");
System.out.println("Exception throws: " + e);
}
}
}
// Java program to demonstrate// arrayOffset() methodimport 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); // Creating a read-only copy of ByteBuffer // using asReadOnlyBuffer() method ByteBuffer bb1 = bb.asReadOnlyBuffer(); // Typecasting read-only ByteBuffer // into read-only Buffer Buffer buffer = (Buffer)bb1; // offset within this buffer's array // of the first element of the buffer // using arrayOffset() method int offset = buffer.arrayOffset(); // print the array System.out.println("arrayOffset is : " + offset); } catch (ReadOnlyBufferException e) { System.out.println("buffer is backed by " + "an array but is read-only"); System.out.println("Exception throws: " + e); } }}
Output:
Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#arrayOffset--
buffer is backed by an array but is read-only Exception throws: java.nio.ReadOnlyBufferException
