The hasArray() method of java.nio.ByteBuffer class is used to ensure whether or not the given buffer is backed by an accessible byte array. It returns true if there is an accessible backing array to this buffer, else it returns false. If this method returns true, then the array() and arrayOffset() methods may safely be invoked, as they work on the backing array.
Syntax:
public final boolean hasArray()
Returns: This method will return true if, and only if, this buffer is backed by an array and is not read-only. Else it returns false.
Below are the examples to illustrate the hasArray() method:
Examples 1: When the buffer is backed by an array
// Java program to demonstrate// hasArray() method  import java.nio.*;import java.util.*;  public class GFG {    public static void main(String[] args)    {          // Declaring the capacity of the ByteBuffer        int capacity = 10;          // 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)10);            bb.put((byte)20);            bb.rewind();              // checking FloatBuffer fb is backed by array or not            boolean isArray = bb.hasArray();              // checking if else condition            if (isArray)                System.out.println("ByteBuffer bb is"                                   + " backed by array");            else                System.out.println("ByteBuffer bb is"                                   + " not backed by any array");        }          catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }          catch (ReadOnlyBufferException e) {            System.out.println("ReadOnlyBufferException catched");        }    }} |
Output:
ByteBuffer bb is backed by array
Examples 2: When the buffer is backed by an array
// Java program to demonstrate// hasArray() method  import java.nio.*;import java.util.*;  public class GFG {      public static void main(String[] args)    {          // Declaring the capacity of the ByteBuffer        int capacity = 10;          // 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)8.56F);            bb.put((byte)10);            bb.rewind();              // Creating a read-only copy of ByteBuffer            // using asReadOnlyBuffer() method            ByteBuffer bb1 = bb.asReadOnlyBuffer();              // checking ByteBuffer bb is backed by array or not            boolean isArray = bb1.hasArray();              // checking if else condition            if (isArray)                System.out.println("ByteBuffer bb is"                                   + " backed by array");            else                System.out.println("ByteBuffer bb is"                                   + " not backed by any array");        }          catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }          catch (ReadOnlyBufferException e) {            System.out.println("ReadOnlyBufferException catched");        }    }} |
Output:
ByteBuffer bb is not backed by any array
Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/ByteBuffer.html#hasArray–
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