Java中的CharBuffer duplicate()方法

Java.nio.CharBuffer类的duplicate()方法用于创建一个共享给定缓冲区内容的新字符缓冲区。

新缓冲区的内容就是这个缓冲区的内容。此缓冲区内容的更改将在新缓冲区中可见，反之亦然；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的相同。当且仅当此缓冲区是直接的时，新缓冲区将是直接的，并且当且仅当此缓冲区是只读的时，它将是只读的。

句法：

public abstract CharBuffer duplicate()

返回值：此方法返回新的字符缓冲区，该缓冲区承载先前的字符缓冲区内容

以下是说明duplicate()方法的示例：

示例 1：使用直接字符缓冲区

// Java program to demonstrate
// duplicate() method
// Using direct intbuffer
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the CharBuffer
        int capacity = 10;
  
        // Creating the CharBuffer
        try {
  
            // creating object of Intbuffer
            // and allocating size capacity
            CharBuffer cb1 = CharBuffer.allocate(capacity);
  
            // putting the value in Intbuffer
            cb1.put('a');
            cb1.put(2, 'b');
            cb1.rewind();
  
            // print the Original CharBuffer
            System.out.println("Original CharBuffer: "
                               + Arrays.toString(cb1.array()));
  
            // Creating a duplicate copy of CharBuffer
            // using duplicate() method
            CharBuffer cb2 = cb1.duplicate();
  
            // print the duplicate copy of CharBuffer
            System.out.print("Duplicate CharBuffer: "
                             + Arrays.toString(cb2.array()));
        }
  
        catch (IllegalArgumentException e) {
  
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
  
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出：

Original CharBuffer: [a, , b, , , , , , , ]
Duplicate CharBuffer: [a, , b, , , , , , , ]

示例 2：使用只读的 intbuffer

// Java program to demonstrate
// duplicate() method
// using read-onlyIntbuffer
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the CharBuffer
        int capacity = 10;
  
        // Creating the CharBuffer
        try {
  
            // creating object of Intbuffer
            // and allocating size capacity
            CharBuffer cb1 = CharBuffer.allocate(capacity);
  
            // putting the value in Intbuffer
            cb1.put('a');
            cb1.put(2, 'b');
            cb1.rewind();
  
            // print the Original CharBuffer
            System.out.println("Original CharBuffer: "
                               + Arrays.toString(cb1.array()));
  
            // Creating a read-only copy of CharBuffer
            // using asReadOnlyBuffer() method
            CharBuffer readonly = cb1.asReadOnlyBuffer();
  
            // print the read-only copy of CharBuffer
            System.out.print("read-only CharBuffer: ");
            while (readonly.hasRemaining())
                System.out.print(readonly.get() + ", ");
            System.out.println("");
  
            // Rewinding the readonly CharBuffer
            readonly.rewind();
  
            // Creating a duplicate copy of CharBuffer
            // using duplicate() method
            CharBuffer cb2 = readonly.duplicate();
  
            // print the duplicate copy of CharBuffer
            System.out.print("duplicate copy of read-only CharBuffer: ");
  
            while (cb2.hasRemaining())
                System.out.print(cb2.get() + ", ");
            System.out.println("");
        }
  
        catch (IllegalArgumentException e) {
  
            System.out.println("IllegalArgumentException catched");
        }
  
        catch (ReadOnlyBufferException e) {
  
            System.out.println("ReadOnlyBufferException catched");
        }
    }
}

输出：

Original CharBuffer: [a, , b, , , , , , , ]
read-only CharBuffer: a, , b, , , , , , , , 
duplicate copy of read-only CharBuffer: a, , b, , , , , , , ,