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Java LineNumberReader mark()用法及代碼示例


LineNumberReader類mark()方法

  • mark() 方法可在java.io包。
  • mark() 方法用於設置此 LineNumberReader 流中的當前位置,每當我們調用 reset() 時,它都會將流重置為最近調用 mark() 方法設置的位置。
  • mark() 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。
  • mark() 方法可能會在標記流時拋出異常。
    IOException:當給定的參數無效時,可能會拋出此異常。

用法:

    public int mark();

參數:

  • int r_limit– 表示在標記失效之前可以讀取的字符數的限製。

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 mark(int r_limit) method of 
// LineNumberReader

import java.io.*;

public class MarkOfLNR {
 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


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注:本文由純淨天空篩選整理自Preeti Jain大神的英文原創作品 Java LineNumberReader mark() Method with Example。非經特殊聲明,原始代碼版權歸原作者所有,本譯文未經允許或授權,請勿轉載或複製。