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.

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