The hasArray() method of java.nio.Buffer class is used to tell whether or not this buffer is backed by an accessible array. If this method returns true then the array and arrayOffset() methods may safely be invoked. Syntax:
public abstract 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 arrayÂ
Java
// Java program to demonstrate// hasArray() methodÂ
import java.nio.*;import java.util.*;Â
public class GFG {Â Â Â Â public static void main(String[] args)Â Â Â Â {Â
        // Declaring the capacity of the ByteBuffer        int capacity = 10;Â
        // Creating the ByteBuffer        try {Â
            // creating object of bytebuffer            // and allocating size capacity            ByteBuffer bb = ByteBuffer.allocate(capacity);Â
            // putting the value in bytebuffer            bb.put((byte)10);            bb.put((byte)20);            bb.rewind();Â
            // Typecast bytebuffer to Buffer            Buffer buffer = (Buffer)bb;Â
            // checking buffer is backed by array or not            boolean isArray = buffer.hasArray();Â
            // checking if else condition            if (isArray)                System.out.println("buffer is"                                   + " backed by array");            else                System.out.println("buffer is"                                   + " not backed by any array");        }Â
        catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }Â
        catch (ReadOnlyBufferException e) {            System.out.println("ReadOnlyBufferException catched");        }    }} |
Output:
buffer is backed by array
Examples 2: When the buffer is not backed by an arrayÂ
Java
// Java program to demonstrate// hasArray() methodÂ
import java.nio.*;import java.util.*;Â
public class GFG {Â
    public static void main(String[] args)    {Â
        // Declaring the capacity of the ByteBuffer        int capacity = 10;Â
        // Creating the ByteBuffer        try {Â
            // creating object of ByteBuffer            // and allocating size capacity            ByteBuffer bb = ByteBuffer.allocate(capacity);Â
            // putting the value in ByteBuffer            bb.put((byte)8.56F);            bb.put((byte)10);            bb.rewind();Â
            // Creating a read-only copy of ByteBuffer            // using asReadOnlyBuffer() method            ByteBuffer bb1 = bb.asReadOnlyBuffer();Â
            // Typecast read-only ByteBuffer to read-only buffer            Buffer buffer = (Buffer)bb1;Â
            // checking buffer is backed by array or not            boolean isArray = buffer.hasArray();Â
            // checking if else condition            if (isArray)                System.out.println("buffer is"                                   + " backed by array");            else                System.out.println("buffer is"                                   + " not backed by any array");        }Â
        catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }Â
        catch (ReadOnlyBufferException e) {            System.out.println("ReadOnlyBufferException catched");        }    }} |
Output:
buffer is not backed by any array
Reference: https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#hasArray–
