Java Buffer duplicate()用法及代码示例

java.nio.Buffer类的duplicate()方法用于创建共享该缓冲区内容的新缓冲区。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，反之亦然；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。当且仅当该缓冲区是直接缓冲区时，新缓冲区才是直接缓冲区；当且仅当该缓冲区是只读缓冲区时，新缓冲区才是只读缓冲区。

用法:

public abstract Buffer duplicate()

返回值：此方法返回承载先前缓冲区内容的新缓冲区。

下面是说明duplicate()方法的示例：

范例1：使用直接ByteBuffer

// Java program to demonstrate 
// duplicate() 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 bb1 
                = ByteBuffer.allocate(capacity); 
  
            // putting the int to byte typecast 
            // value in ByteBuffer 
            bb1.put((byte)20); 
            bb1.put((byte)30); 
            bb1.put((byte)40); 
            bb1.put((byte)50); 
            bb1.rewind(); 
  
            // print the Original ByteBuffer 
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb1.array())); 
  
            // Creating a duplicate copy of ByteBuffer 
            // using duplicate() method 
            ByteBuffer bb2 = bb1.duplicate(); 
  
            // print the duplicate copy of ByteBuffer 
            System.out.print("\nDuplicate ByteBuffer: "
                             + Arrays.toString(bb2.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]

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

范例2：使用只读ByteBuffer

// Java program to demonstrate 
// duplicate() 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 bb1 
                = ByteBuffer.allocate(capacity); 
  
            // putting the int to byte typecast 
            // value in ByteBuffer 
            bb1.put((byte)20); 
            bb1.put((byte)30); 
            bb1.put((byte)40); 
            bb1.put((byte)50); 
            bb1.rewind(); 
  
            // print the Original ByteBuffer 
            System.out.println("Original ByteBuffer:  "
                               + Arrays.toString(bb1.array())); 
  
            // Creating a read-only copy of ByteBuffer 
            // using asReadOnlyBuffer() method 
            ByteBuffer readonly = bb1.asReadOnlyBuffer(); 
  
            // print the read-only copy of ByteBuffer 
            System.out.print("\nRead-only ByteBuffer:  "); 
            while (readonly.hasRemaining()) 
                System.out.print(readonly.get() + ", "); 
            System.out.println(""); 
  
            // Rewinding the readonly ByteBuffer 
            readonly.rewind(); 
  
            // Creating a duplicate copy of ByteBuffer 
            // using duplicate() method 
            ByteBuffer bb2 = readonly.duplicate(); 
  
            // print the duplicate copy of ByteBuffer 
            System.out.print("\nDuplicate copy of "
                             + "read-only ByteBuffer:  "); 
  
            while (bb2.hasRemaining()) 
                System.out.print(bb2.get() + ", "); 
            System.out.println(""); 
        } 
  
        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]

Read-only ByteBuffer:  20, 30, 40, 50, 

Duplicate copy of read-only ByteBuffer:  20, 30, 40, 50,

参考： https://docs.oracle.com/javase/9/docs/api/java/nio/Buffer.html#duplicate–

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 Buffer duplicate() 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。