Java ByteBuffer array()方法及示例

java.nio.ByteBuffer 类的 array() 方法用于返回支持所取缓冲区的字节数组。

对该缓冲区内容的修改将导致返回的数组内容被修改，反之亦然。

在调用该方法之前调用hasArray()方法，以确保该缓冲区有一个可访问的支持阵列。

语法:

public final byte[] array()

返回值： 该方法返回支持该缓冲区的数组。

异常： 该方法抛出ReadOnlyBufferException，如果该缓冲区是由数组支持的但却是只读的。

下面是一些例子来说明array()方法。

例1 :

// Java program to demonstrate
// array() 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);
 
            // print the ByteBuffer
            System.out.println("ByteBuffer:  "
                               + Arrays.toString(bb.array()));
 
            // getting byte array from ByteBuffer
            // using array() method
            byte[] arr = bb.array();
 
            // print the byte array
            System.out.println("\nbyte array: " +
                                    Arrays.toString(arr));
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception throws: " + e);
        }
    }
}

输出

ByteBuffer:  [20, 30, 40, 50]

byte array: [20, 30, 40, 50]

例2 :

// Java program to demonstrate
// array() 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("Original ByteBuffer:  "
                               + Arrays.toString(bb.array()));
 
            // Creating a read-only copy of ByteBuffer
            // using asReadOnlyBuffer() method
            ByteBuffer bb1 = bb.asReadOnlyBuffer();
            bb1.rewind();
 
            // print the ByteBuffer
            System.out.print("\nReadOnlyBuffer ByteBuffer : ");
 
            while (bb1.hasRemaining())
                System.out.print(bb1.get() + ", ");
 
            // getting byte array from read-only
            // ByteBuffer using array() method
            System.out.println("\n\nTrying to get the array"
                               + " from bb1 for editing");
            byte[] arr = bb1.array();
        }
 
        catch (IllegalArgumentException e) {
 
            System.out.println("Exception throws: " + e);
        }
 
        catch (ReadOnlyBufferException e) {
 
            System.out.println("Exception throws: " + e);
        }
    }
}

输出

Original ByteBuffer:  [20, 30, 40, 50]

ReadOnlyBuffer ByteBuffer : 20, 30, 40, 50, 

Trying to get the array from bb1 for editing
Exception throws: java.nio.ReadOnlyBufferException