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Java FilterReader mark() Method with Example

FilterReader Class mark() method: Here, we are going to learn about the mark() method of FilterReader Class with its syntax and example.
Submitted by Preeti Jain, on April 03, 2020

FilterReader Class mark() method

• mark() method is available in java.io package.
• mark() method is used to mark the current position in this FilterReader stream.
• mark() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• mark() method may throw an exception at the time of marking the stream.
  IOException: This exception may throw when the given parameter is invalid.

Syntax:

    public void mark(int r_limit);

Parameter(s):

• int r_limit – represents limit on the number of characters that may be read while preserving the mark.

Return value:

The return type of the method is void, it returns nothing.

Example:

// 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();
   }
  }
 }
}

Output

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