Java LineNumberReader reset()用法及代碼示例

LineNumberReader類reset()方法

• reset() 方法可在java.io包。
• reset() 方法用於將此 LineNumberReader 流重置為通過調用其 mark() 方法設置的最新標記的位置。
• reset() 方法是一個非靜態方法，它隻能通過類對象訪問，如果我們嘗試使用類名訪問方法，那麽我們將得到一個錯誤。
• reset() 方法可能會在重置流時拋出異常。
  IOException：當此流尚未標記或設置標記無效時，可能會拋出此異常。

用法:

    public void reset();

參數：

• 它不接受任何參數。

返回值：

該方法的返回類型是void，它什麽都不返回。

例：

// Java program to demonstrate the example 
// of void reset() method of LineNumberReader

import java.io.*;

public class ResetOfLNR {
 public static void main(String[] args) throws Exception {
  FileReader fr_stm = null;
  LineNumberReader line_r = null;
  int val = 0;

  try {
   // Instantiates FileReader and LineNumberReader
   fr_stm = new FileReader("D:\\includehelp.txt");
   line_r = new LineNumberReader(fr_stm);

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

   System.out.println("line_r.mark(0):");
   line_r.mark(0);
   char ch4 = (char) line_r.read();
   char ch5 = (char) line_r.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_r.reset():");
   line_r.reset();
   char ch6 = (char) line_r.read();
   char ch7 = (char) line_r.read();
   char ch8 = (char) line_r.read();
   char ch9 = (char) line_r.read();
   char ch10 = (char) line_r.read();
   char ch11 = (char) line_r.read();


   System.out.println("ch4:" + ch6);
   System.out.println("ch5:" + ch7);
   System.out.println("ch6:" + ch8);
   System.out.println("ch7:" + ch9);
   System.out.println("ch8:" + ch10);
   System.out.println("ch9:" + ch11);

  } 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 (fr_stm != null) {
    fr_stm.close();
    if (line_r != null) {
     line_r.close();
    }
   }
  }
 }
}

輸出

ch1:J
ch2:A
ch3:V
line_r.mark(0):
ch4:A
ch5:W
line_r.reset():
ch4:A
ch5:W
ch6:O
ch7:R
ch8:L
ch9:D