PushbackReader read(char[], int, int) in Java

read(char[], int, int): This method is available in the java.io.PushbackReader class of Java.

Syntax:

int java.io.PushbackReader.read(char[] cbuf, int off, int len) throws IOException

This method takes three arguments. This method reads characters into a portion of an array.

Parameters: Three parameters are required for this method.

cbuf: Destination buffer.

off: Offset at which to start writing characters.

len: Maximum number of characters to read.

Returns: The number of characters reads, or -1 if the end of the stream has been reached.

Throws:

1. IOException - If an I/O error occurs.

2. IndexOutOfBoundsException - If off is negative, or len is negative, or len is greater than cbuf.length - off

Approach 1: When no exception

Java

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

public class PushbackReaderread2 {
    public static void main(String[] args) throws IOException {

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

        char cbuf[] = { 'a', 'b', 'c', 'd', 'e' };
        int off = 0, len = 3;

        System.out.println(pushbackReader.read(cbuf, off, len));

        pushbackReader.close();
    }
}

Output:

3

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 PushbackReaderread2 {
    public static void main(String[] args) throws IOException {

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

        char cbuf[] = { 'a', 'b', 'c', 'd', 'e' };
        int off = 0, len = 3;

        System.out.println(pushbackReader.read(cbuf, off, len));

        pushbackReader.close();
    }
}

Output:

Exception in thread "main" java.io.IOException: Pipe not connected
	at java.base/java.io.PipedReader.read(PipedReader.java:293)
	at java.base/java.io.FilterReader.read(FilterReader.java:75)
	at java.base/java.io.PushbackReader.read(PushbackReader.java:129)
	at com.PushbackReader.PushbackReaderread2.main(PushbackReaderread2.java:17)

Approach 3: IndexOutOfBoundsException 

Java

package com.PushbackReader;

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

public class PushbackReaderread2 {
    public static void main(String[] args) throws IOException {

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

        char cbuf[] = { 'a', 'b', 'c', 'd', 'e' };
        int off = 0, len = 13;

        System.out.println(pushbackReader.read(cbuf, off, len));

        pushbackReader.close();
    }
}

Output:

Exception in thread "main" java.lang.IndexOutOfBoundsException
	at java.base/java.io.StringReader.read(StringReader.java:94)
	at java.base/java.io.FilterReader.read(FilterReader.java:75)
	at java.base/java.io.PushbackReader.read(PushbackReader.java:129)
	at com.PushbackReader.PushbackReaderread2.main(PushbackReaderread2.java:17)

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.