Reader read(CharBuffer) method in Java with Examples

Last Updated : 07 Feb, 2019

The read(CharBuffer) method of Reader Class in Java is used to read the specified characters into a CharBuffer instance. This method blocks the stream till:

It has taken some input from the stream.
Some IOException has occurred
It has reached the end of the stream while reading.

Syntax:

public int read(CharBuffer charBuffer)

Parameters: This method accepts a mandatory parameter charBuffer which is the CharBuffer instance to be written in the Stream. Return Value: This method returns an integer value which is the number of characters read from the stream. It returns -1 if no character has been read. Exception: This method throws following exceptions:

IOException: if some error occurs while input output.
NullPointerException: if the CharBuffer instance to be filled is null
ReadOnlyBufferException: if the CharBuffer instance to be filled is a read only buffer

Below methods illustrates the working of read(CharBuffer) method: Program 1:

Java

// Java program to demonstrate
// Reader read(CharBuffer) method

import java.io.*;
import java.util.*;
import java.nio.CharBuffer;

class GFG {
    public static void main(String[] args)
    {

        try {

            String str = "GeeksForGeeks";

            // Create a Reader instance
            Reader reader
                = new StringReader(str);

            // Get the CharBuffer instance
            // to be read from the stream
            CharBuffer charBuffer
                = CharBuffer.allocate(5);

            // Read the charBuffer
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            reader.read(charBuffer);

            // Print the read charBuffer
            System.out.println(charBuffer
                                   .flip()
                                   .toString());

            reader.close();
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output:

Geeks

Program 2:

Java

// Java program to demonstrate
// Reader read(CharBuffer) method

import java.io.*;
import java.util.*;
import java.nio.CharBuffer;

class GFG {
    public static void main(String[] args)
    {

        try {

            String str = "GeeksForGeeks";

            // Create a Reader instance
            Reader reader
                = new StringReader(str);

            // Get the CharBuffer instance
            // to be read from the stream
            CharBuffer charBuffer
                = CharBuffer
                      .allocate(
                          str.length());

            // Read the charBuffer
            // to this reader using read() method
            // This will put the str in the stream
            // till it is read by the reader
            reader.read(charBuffer);

            // Print the read charBuffer
            System.out.println(charBuffer
                                   .flip()
                                   .toString());

            reader.close();
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}