PushbackReader ready() in Java

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

Syntax:

boolean java.io.PushbackReader.ready() throws IOException

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

Parameters: NA

Returns: True if the next read() is guaranteed not to block for input,false  otherwise.

Note that returning false does not guarantee that the next read will block.

Throws:

IOException - If an I/O error occurs

Approach 1: When no exception

Java

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

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

        Reader in = new StringReader("HELLO");
        PushbackReader pushbackReader = new PushbackReader(in);

        System.out.println(pushbackReader.ready());

        pushbackReader.close();
    }
}

Output:

true

Approach 2: IOException 

Java

package com.PushbackReader;

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

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

        Reader in = new PipedReader();
        PushbackReader pushbackReader = new PushbackReader(in);

        System.out.println(pushbackReader.ready());

        pushbackReader.close();
    }
}

Output:

Exception in thread "main" java.io.IOException: Pipe not connected
	at java.base/java.io.PipedReader.ready(PipedReader.java:339)
	at java.base/java.io.FilterReader.ready(FilterReader.java:93)
	at java.base/java.io.PushbackReader.ready(PushbackReader.java:208)
	at com.PushbackReader.PushbackReaderready.main(PushbackReaderready.java:14)

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.