Java ByteBuffer asReadOnlyBuffer()用法及代码示例

java.nio.ByteBuffer类的asReadOnlyBuffer()方法用于创建共享该缓冲区内容的新的只读字节缓冲区。

新缓冲区的内容就是该缓冲区的内容。对该缓冲区内容的更改将在新缓冲区中可见；但是，新缓冲区本身将是只读的，并且不允许修改共享内容。这两个缓冲区的位置，限制和标记值将是独立的。

新缓冲区的容量，限制，位置和标记值将与此缓冲区相同。

如果此缓冲区本身是只读的，则此方法的行为与重复方法完全相同。

用法:

public abstract ByteBuffer asReadOnlyBuffer()

返回值：此方法返回新的只读字节缓冲区，其内容与此缓冲区的内容相同。

下面是说明asReadOnlyBuffer()方法的示例：

范例1：

// Java program to demonstrate 
// asReadOnlyBuffer() 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(); 
  
            // print the ByteBuffer 
            System.out.print("\nReadOnlyBuffer ByteBuffer: "); 
  
            while (bb1.hasRemaining()) 
                System.out.print(bb1.get() + ", "); 
        } 
  
        catch (IllegalArgumentException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
  
        catch (ReadOnlyBufferException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

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

ReadOnlyBuffer ByteBuffer: 20, 30, 40, 50,

范例2：

// Java program to demonstrate 
// asReadOnlyBuffer() 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(); 
  
            // print the ByteBuffer 
            System.out.print("\nReadOnlyBuffer ByteBuffer: "); 
  
            while (bb1.hasRemaining()) 
                System.out.print(bb1.get() + ", "); 
  
            // try to change read only bytebuffer 
            System.out.println("\n\nTrying to get the array"
                               + " from bb1 for editing"); 
  
            byte[] bbarr = bb1.array(); 
        } 
  
        catch (IllegalArgumentException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
  
        catch (ReadOnlyBufferException e) { 
  
            System.out.println("Exception thrown : " + 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 thrown : java.nio.ReadOnlyBufferException

相关用法

注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 ByteBuffer asReadOnlyBuffer() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。