Java.io.FilterReader.mark() Method

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Description

The java.io.FilterReader.mark(int readAheadLimit) method marks the present position of the stream.

Declaration

Following is the declaration for java.io.FilterReader.mark(int readAheadLimit) method −

public void mark(int readAheadLimit)

Parameters

readAheadLimit − Limit on the number of characters that may be read while still preserving the mark.

Return Value

This method does not return any value.

Exception

IOException − If an I/O error occurs.

Example

The following example shows the usage of java.io.FilterReader.mark(int readAheadLimit) method.

package com.tutorialspoint;

import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;

public class FilterReaderDemo {
   public static void main(String[] args) throws Exception {
      FilterReader fr = null;
      Reader r = null;      
      
      try {
         // create new reader
         r = new StringReader("ABCDEF");
          
         // create new filter reader
         fr = new FilterReader(r) {
         };
         
         // reads and prints FilterReader
         System.out.println((char)fr.read());
         System.out.println((char)fr.read());
                  
         // mark invoked at this position
         fr.mark(0);
         System.out.println("mark() invoked");
         System.out.println((char)fr.read());
         System.out.println((char)fr.read());
                  
         // reset() repositioned the stream to the mark
         fr.reset();
         System.out.println("reset() invoked");
         System.out.println((char)fr.read());
         System.out.println((char)fr.read());
         
      } catch(IOException e) {
         // if any I/O error occurs
         e.printStackTrace();
      } finally {
         // releases system resources associated with this stream
         if(r!=null)
            r.close();
         if(fr!=null)
            fr.close();
      }
   }
}

Let us compile and run the above program, this will produce the following result −

A
B
mark() invoked
C
D
reset() invoked
C
D