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Java PushbackInputStream mark() Method with Example

PushbackInputStream Class mark() method: Here, we are going to learn about the mark() method of PushbackInputStream Class with its syntax and example.
Submitted by Preeti Jain, on April 20, 2020

PushbackInputStream Class mark() method

• mark() method is available in java.io package.
• mark() method is used to set the current position in this PushbackInputStream 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 does not throw an exception at the time of marking the stream.

Syntax:

    public void mark(int r_limit);

Parameter(s):

• int r_limit – represents maximum limit of bytes that can be read before the mark gets invalid.

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
// PushbackInputStream

import java.io.*;

public class MarkOfPBIS {
    public static void main(String[] args) throws Exception {
        byte[] b_arr = {
            97,
            98,
            99,
            100
        };
        int count = 0;
        InputStream is_stm = null;
        PushbackInputStream pb_stm = null;

        try {
            // Instantiates ByteArrayOutputStream and PushbackInputStream
            is_stm = new ByteArrayInputStream(b_arr);
            pb_stm = new PushbackInputStream(is_stm);

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

            System.out.println("ch1: " + ch1);
            System.out.println("ch2: " + ch2);

            // By using mark() method isto
            // set the current position in this
            // pb_stm

            System.out.println("pb_stm.mark(1): ");
            pb_stm.mark(1);
            char ch4 = (char) pb_stm.read();
            char ch5 = (char) pb_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("pb_stm.reset(): ");
            pb_stm.reset();
            char ch6 = (char) pb_stm.read();
            char ch7 = (char) pb_stm.read();
            char ch8 = (char) pb_stm.read();

            System.out.println("ch4: " + ch6);
            System.out.println("ch5: " + ch7);
            System.out.println("ch6: " + ch8);
        } catch (Exception ex) {
            System.out.println("Mark Not Supported");
        } finally {
            if (is_stm != null)
                is_stm.close();
            if (pb_stm != null)
                pb_stm.close();
        }
    }
}

Output

ch1: a
ch2: b
pb_stm.mark(1): 
ch4: c
ch5: d
pb_stm.reset(): 
Mark Not Supported