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CharArrayReader mark(int) method in Java with Examples

Last Updated : 11 Jul, 2025
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The mark() method of CharArrayReader Class in Java is used to mark the stream as the checkpoint from where the stream read will start, once reset() is called. This method is not supported by all subclasses of CharArrayReader class. Syntax: 
public void mark(int readAheadLimit)
Parameters: This method accepts a mandatory parameter readAheadLimit which is the limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail. Return Value: This method do not returns any value. Exception: This method throws IOException if some error occurs while input output or the mark() method is not supported. Below methods illustrates the working of mark() method: Program 1: Java 
// Java program to demonstrate
// CharArrayReader mark() method

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        try {

            char[] str = { 'G', 'e', 'e', 'k', 's',
                           'F', 'o', 'r',
                           'G', 'e', 'e', 'k', 's' };

            // Create a CharArrayReader instance
            CharArrayReader reader
                = new CharArrayReader(str);

            // Get the character
            // to be read from the stream
            int ch;

            // Read the first 10 characters
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            for (int i = 0; i < 10; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }

            System.out.println();

            // mark the stream for
            // 5 characters using mark()
            reader.mark(5);

            // reset the stream position
            reader.reset();

            // Read the 5 characters from marked position
            // to this reader using read() method
            for (int i = 0; i < 5; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}
Output: 
GeeksForGe
eks??
Program 2: Java 
// Java program to demonstrate
// CharArrayReader mark() method

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        try {
            char[] str = { 'G', 'e', 'e', 'k',
                           's', 'F', 'o', 'r',
                           'G', 'e', 'e', 'k', 's' };

            // Create a CharArrayReader instance
            CharArrayReader reader
                = new CharArrayReader(str);

            // Get the character
            // to be read from the stream
            int ch;

            // Read the first 10 characters
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            for (int i = 0; i < 10; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }

            System.out.println();

            // mark the stream for
            // 10 characters using mark()
            reader.mark(10);

            // reset the stream position
            reader.reset();

            // Read the 1 characters from marked position
            // to this reader using read() method
            for (int i = 0; i < 1; i++) {
                ch = reader.read();
                System.out.print((char)ch);
            }
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}
Output: 
GeeksForGe
e
Reference: https://docs.oracle.com/javase/9/docs/api/java/io/CharArrayReader.html#mark-int-

C

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