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PushbackInputStream mark() method in Java with Examples

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  • Last Updated : 16 Jun, 2022

The mark() method of PushbackInputStream class in Java is used to mark the current position in the input stream. This method does nothing for PushbackInputStream. 

Syntax:

public void mark(int readlimit)

Overrides: This method overrides the mark() method of FilterInputStream class. 

Parameters: This method accepts single parameter readlimit that represents the maximum limit of bytes that can be read before the mark position becomes invalid. 

Return value: This method does not return any value. 

Exceptions: This method does not throw any exception. 

Below programs illustrate mark() method of PushbackInputStream class in IO package: 

Program 1: 

Java




// Java program to illustrate
// PushbackInputStream mark() method
 
import java.io.*;
 
public class GFG {
    public static void main(String[] args)
        throws IOException
    {
 
        // Create an array
        byte[] byteArray
            = new byte[] { 'G', 'E', 'E',
                           'K', 'S' };
 
        // Create inputStream
        InputStream inputStr
            = new ByteArrayInputStream(byteArray);
 
        // Create object of
        // PushbackInputStream
        PushbackInputStream pushbackInputStr
            = new PushbackInputStream(inputStr);
 
        for (int i = 0; i < byteArray.length; i++) {
            // Read the character
            System.out.print(
                (char)pushbackInputStr.read());
        }
 
        // Revoke mark() but it does nothing
        pushbackInputStr.mark(5);
    }
}

Output:

GEEKS

Program 2: 

Java




// Java program to illustrate
// PushbackInputStream mark() method
 
import java.io.*;
 
public class GFG {
    public static void main(String[] args)
        throws IOException
    {
 
        // Create an array
        byte[] byteArray
            = new byte[] { 'H', 'E', 'L',
                           'L', 'O' };
 
        // Create inputStream
        InputStream inputStr
            = new ByteArrayInputStream(byteArray);
 
        // Create object of
        // PushbackInputStream
        PushbackInputStream pushbackInputStr
            = new PushbackInputStream(inputStr);
 
        // Revoke mark()
        pushbackInputStr.mark(1);
 
        for (int i = 0; i < byteArray.length; i++) {
            // Read the character
            System.out.print(
                (char)pushbackInputStr.read());
        }
    }
}

Output:

HELLO

References: https://docs.oracle.com/javase/10/docs/api/java/io/PushbackInputStream.html#mark(int)


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