Java LineNumberInputStream mark()用法及代码示例

LineNumberInputStream类mark()方法

• mark() 方法可在java.io包。
• mark() 方法用于设置此 LineNumberInputStream 中的当前位置，后续调用 reset 会将流重置为最近调用 mark() 方法标记的位置。
• mark() 方法是一个非静态方法，它只能通过类对象访问，如果我们尝试使用类名访问方法，那么我们将得到一个错误。
• mark() 方法在标记流时不会抛出异常。

用法:

    public void mark(int r_limit);

参数：

• int r_limit– 表示在 mark() 位置无效之前可以读取的最大字节数。

返回值：

该方法的返回类型是void，它什么都不返回。

例：

// Java program to demonstrate the example 
// of void mark(int r_limit) method of 
// LineNumberInputStream

import java.io.*;

public class MarkOfLNIS {
 public static void main(String[] args) throws Exception {
  FileInputStream fis_stm = null;
  LineNumberInputStream line_stm = null;
  int val = 0;

  try {
   // Instantiates FileInputStream
   fis_stm = new FileInputStream("D:\\includehelp.txt");
   line_stm = new LineNumberInputStream(fis_stm);

   // By using read() method isto 
   // read the character from line_stm
   char ch1 = (char) line_stm.read();
   char ch2 = (char) line_stm.read();
   char ch3 = (char) line_stm.read();

   System.out.println("ch1:" + ch1);
   System.out.println("ch2:" + ch2);
   System.out.println("ch3:" + ch3);

   // By using mark() method isto
   // set the current position in this
   // line_stm

   System.out.println("line_stm.mark(0):");
   line_stm.mark(0);
   char ch4 = (char) line_stm.read();
   char ch5 = (char) line_stm.read();

   System.out.println("ch4:" + ch4);
   System.out.println("ch5:" + ch5);
   // By using reset() method isto
   // reset the stream to the position 
   // set by the call mark() method

   System.out.println("line_stm.reset():");
   line_stm.reset();
   char ch6 = (char) line_stm.read();
   char ch7 = (char) line_stm.read();
   char ch8 = (char) line_stm.read();
   char ch9 = (char) line_stm.read();


   System.out.println("ch4:" + ch6);
   System.out.println("ch5:" + ch7);
   System.out.println("ch6:" + ch8);
   System.out.println("ch7:" + ch9);

  } catch (Exception ex) {
   System.out.println(ex.toString());
  } finally {
   // with the help of this block is to
   // free all necessary resources linked
   // with the stream
   if (fis_stm != null) {
    fis_stm.close();
    if (line_stm != null) {
     line_stm.close();
    }
   }
  }
 }
}

输出

ch1:J
ch2:A
ch3:V
line_stm.mark(0):
ch4:A
ch5:W
line_stm.reset():
java.io.IOException:mark/reset not supported