Java中的 ByteBuffer array() 方法及示例

Java.nio.ByteBuffer类的array()方法用于返回支持所获取缓冲区的字节数组。
对此缓冲区内容的修改将导致返回数组的内容被修改，反之亦然。
在调用此方法之前调用 hasArray() 方法，以确保此缓冲区具有可访问的后备数组。

句法 ：

public final byte[] array()

返回值：此方法返回支持此缓冲区的数组。
异常：此方法抛出ReadOnlyBufferException ，如果此缓冲区由数组支持但为只读。

以下是说明 array() 方法的示例：

示例 1：

Java

// 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]

示例 2：

Java

// 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