Java Buffer duplicate()用法及代碼示例

java.nio.Buffer類的duplicate()方法用於創建共享該緩衝區內容的新緩衝區。新緩衝區的內容就是該緩衝區的內容。對該緩衝區內容的更改將在新緩衝區中可見，反之亦然；這兩個緩衝區的位置，限製和標記值將是獨立的。新緩衝區的容量，限製，位置和標記值將與此緩衝區相同。當且僅當該緩衝區是直接緩衝區時，新緩衝區才是直接緩衝區；當且僅當該緩衝區是隻讀緩衝區時，新緩衝區才是隻讀緩衝區。

用法:

public abstract Buffer duplicate()

返回值：此方法返回承載先前緩衝區內容的新緩衝區。

下麵是說明duplicate()方法的示例：

範例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); 
        } 
    } 
}

輸出：

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

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

範例2：使用隻讀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); 
        } 
    } 
}

輸出：

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

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

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

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

相關用法

注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 Buffer duplicate() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。