Java FilterReader mark()用法及代碼示例

FilterReader類mark()方法

• mark() 方法可在java.io包。
• mark() 方法用於標記此 FilterReader 流中的當前位置。
• 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 void mark(int r_limit);

參數：

• int r_limit– 表示在保留標記的同時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 FilterReader

import java.io.*;

public class MarkOfFR {
 public static void main(String[] args) throws Exception {
  Reader r_stm = null;
  FilterReader fr_stm = null;

  try {
   // Instantiates StringReader and 
   // FilterReader
   r_stm = new StringReader("JavaWorld!!!!");
   fr_stm = new FilterReader(r_stm) {};

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

   System.out.println("fr_stm.mark(1):");
   fr_stm.mark(1);
   char ch4 = (char) fr_stm.read();
   char ch5 = (char) fr_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("fr_stm.reset():");
   fr_stm.reset();
   char ch6 = (char) fr_stm.read();
   char ch7 = (char) fr_stm.read();
   char ch8 = (char) fr_stm.read();
   char ch9 = (char) fr_stm.read();
   char ch10 = (char) fr_stm.read();
   char ch11 = (char) fr_stm.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();
   }
  }
 }
}

輸出

ch1:J
ch2:a
ch3:v
fr_stm.mark(1):
ch4:a
ch5:W
fr_stm.reset():
ch4:a
ch5:W
ch6:o
ch7:r
ch8:l
ch9:d