Java CharBuffer clear()方法及示例

java.nio.CharBuffer 类的 clear() 方法被用来清除这个缓冲区。位置被设置为零，极限被设置为容量，并且标记被丢弃。在使用一连串的channel-read或put操作来填充这个缓冲区之前调用这个方法。

例如 。

// Prepare buffer for reading
buf.clear();

// Read data
in.read(buf);

这个方法实际上并不清除缓冲区中的数据，但它被命名为仿佛清除了数据，因为它最常被用于可能是这种情况的场合。

语法

public final CharBuffer clear()

返回值： 该方法返回这个缓冲区。

下面是说明clear()方法的例子。

例子 1 :

// Java program to demonstrate
// clear() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            char[] carr = { 'a', 'b', 'c', 'd' };
  
            // creating object of CharBuffer
            // and allocating size capacity
            CharBuffer cb = CharBuffer.wrap(carr);
  
            // try to set the position at index 2
            cb.position(2);
  
            // Set this buffer mark position
            // using mark() method
            cb.mark();
  
            // try to set the position at index 4
            cb.position(4);
  
            // display position
            System.out.println("position before reset: "
                               + cb.position());
  
            // try to call clear() to restore
            // to the position at index 0
            // by discarding the mark
            cb.clear();
  
            // display position
            System.out.println("position after reset: "
                               + cb.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("new position is less than "
                               + "the position we "
                               + "marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

输出:

position before reset: 4
position after reset: 0

例子 2 :

// Java program to demonstrate
// clear() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        char[] carr = { '.', '<', '@', 'a' };
  
        // creating object of CharBuffer
        // and allocating size capacity
        CharBuffer cb = CharBuffer.wrap(carr);
  
        // try to set the position at index 2
        cb.position(3);
  
        // display position
        System.out.println("position before clear: "
                           + cb.position());
  
        // try to call clear() to restore
        // to the position at index 0
        // by discarding the mark
        cb.clear();
  
        // display position
        System.out.println("position after clear: "
                           + cb.position());
    }
}

输出:

position before clear: 3
position after clear: 0

参考资料: https://docs.oracle.com/javase/9/docs/api/java/nio/CharBuffer.html#clear-