Java CharBuffer mark()方法及示例

java.nio.CharBuffer类的 mark() 方法用于在其位置上设置该缓冲区的标记。

语法

public CharBuffer mark()

返回值： 该方法返回这个缓冲区。

下面是说明mark()方法的例子。

例子 1 :

// Java program to demonstrate
// mark() 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 reset() to restore
            // to the position we marked
            cb.reset();
  
            // 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: 2

实例2： 演示InvalidMarkException

// Java program to demonstrate
// mark() 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(1);
  
            // display position
            System.out.println("position before reset: "
                               + cb.position());
  
            // try to call reset() to restore
            // to the position we marked
            cb.reset();
  
            // display position
            System.out.println("position after reset: "
                               + cb.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("\nnew position is less than "
                               + "the position we marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

输出:

position before reset: 1

new position is less than the position we marked before 
Exception throws: java.nio.InvalidMarkException

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