PushbackReader PushbackReader(Reader, int) in Java

PushbackReader(Reader, int): This method is available in the java.io.PushbackReader class of Java.

Syntax:

java.io.PushbackReader.PushbackReader(Reader in, int size)

This method takes two arguments. This method creates a new pushback reader with a pushback buffer of the given size.

Parameters: Two parameters are required for this method.

in: The reader from which characters will be read.

size: The size of the pushback buffer.

Throws:

1. IllegalArgumentException - if size <= 0

Approach 1: When no exception

Java

import java.io.IOException;
import java.io.PipedReader;
import java.io.PushbackReader;
import java.io.Reader;

public class PushbackReaderPushbackReader2 {
    public static void main(String[] args) throws IOException {

        Reader in = new PipedReader();
        int size = 10;
        PushbackReader pushbackReader = 
                      new PushbackReader(in, size);

        System.out.println(pushbackReader);
        pushbackReader.close();
    }
}

Output:

java.io.PushbackReader@7637f22

Approach 2: IllegalArgumentException 

Java

package com.PushbackReader;

import java.io.IOException;
import java.io.PipedReader;
import java.io.PushbackReader;
import java.io.Reader;

public class PushbackReaderPushbackReader2 {
    public static void main(String[] args) throws IOException {

        Reader in = new PipedReader();
        int size = -10;
        PushbackReader pushbackReader = 
                         new PushbackReader(in, size);

        System.out.println(pushbackReader);
        pushbackReader.close();
    }
}

Output:

Exception in thread "main" java.lang.IllegalArgumentException: size <= 0
	at java.base/java.io.PushbackReader.<init>(PushbackReader.java:55)
	at com.PushbackReader.PushbackReaderPushbackReader2.main(PushbackReaderPushbackReader2.java:13)

Some other methods of PushbackReader

close(): This method closes the stream and releases any system resources associated with it.

mark(int): This method marks the present position in the stream.

markSupported(): This method tells whether this stream supports the mark() operation, which it does not.

PushbackReader(Reader): This method creates a new pushback reader with a one-character pushback buffer.

PushbackReader(Reader, int): This method creates a new pushback reader with a pushback buffer of the given size.

read(): This method reads a single character.

read(char[], int, int): This method reads characters into a portion of an array.

ready(): This method tells whether this stream is ready to be read.

reset(): This method resets the stream.

skip(long): This method skips characters

unread(char[]): This method pushes back an array of characters by copying it to the front of the pushback buffer.

unread(int): This method pushes back a single character by copying it to the front of the pushback buffer.

unread(char[], int, int):  This method pushes back a portion of an array of characters by copying it to the front of the pushback buffer.