Java中的 CharBuffer rewind() 方法及示例

Java.nio.CharBuffer 类的rewind()方法用于倒带这个缓冲区。位置设置为零并且标记被丢弃。在一系列通道写入或获取操作之前调用此方法，假设已经适当地设置了限制。调用此方法既不会更改也不会丢弃标记的值。

句法：

public ByteBuffer rewind()

返回值：此方法返回此缓冲区。

以下是说明 rewind() 方法的示例：

示例 1：

// Java program to demonstrate
// rewind() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating CharBuffer
        // using allocate() method
        CharBuffer charBuffer = CharBuffer.allocate(4);
  
        // put char value in charBuffer
        // using put() method
        charBuffer.put('a');
        charBuffer.put((char)105);
  
        // print the char buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
  
        // rewind the Buffer
        // using rewind() method
        charBuffer.rewind();
  
        // print the charbuffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
    }
}

输出：

Buffer before operation: [a, i,,  ]
Position: 2
Limit: 4

Buffer after operation: [a, i,,  ]
Position: 0
Limit: 4

示例 2：

// Java program to demonstrate
// rewind() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
        // defining and allocating CharBuffer
        // using allocate() method
        CharBuffer charBuffer
            = CharBuffer.allocate(5);
  
        // put byte value in charBuffer
        // using put() method
        charBuffer.put('a');
        charBuffer.put('b');
        charBuffer.put('c');
  
        // mark will be going to discarded by rewind()
        charBuffer.mark();
  
        // print the buffer
        System.out.println("Buffer before operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
  
        // Rewind the Buffer
        // using rewind() method
        charBuffer.rewind();
  
        // print the buffer
        System.out.println("\nBuffer after operation: "
                           + Arrays.toString(
                                 charBuffer.array())
                           + "\nPosition: "
                           + charBuffer.position()
                           + "\nLimit: "
                           + charBuffer.limit());
    }
}

输出：

Buffer before operation: [a, b, c,,  ]
Position: 3
Limit: 5

Buffer after operation: [a, b, c,,  ]
Position: 0
Limit: 5

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/CharBuffer.html#rewind–