Java BufferedReader Class Example

In this article, we are going to learn about the BufferedReader class in Java, its uses and a simple program to showcase how to read data using BufferedReader and readline() method.

1. What is BufferedReader

BufferedReader provides a way to seamlessly read characters from an Input Stream. InputStream can be an instance of a File or System IO or a Socket. BufferedReader improves the IO reading performance by maintaining an internal buffer. Internal buffer stores chunks of data and the Reader reads from it instead of reading directly from the underlying physical IO system.

2. BufferedReader constructors

BufferedReader offers below overloaded constructors,

• BufferedReader(Reader in) – Creates a buffered input stream with default buffer size
• BufferedReader(Reader in, int size) – Users buffer of specified size

Use the appropriate constructor based on your use case.

3. BufferedReader methods

In this section, I am going to list some of the useful methods that are part of BufferedReader class.

4. Java BufferedReader Class Example

4.1 Reading from the console

In this example, I am going to show how you can read from the console using the BufferedReader class.

BufferedReaderConsoleRead.java

package com.jcg;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class BufferedReaderConsoleRead {
    public static void main(String[] args) throws IOException {
        //Enter data to BufferedReader from console
        System.out.println("Enter your name : ");
        BufferedReader reader =
                new BufferedReader(new InputStreamReader(System.in));

        // Reading data using readLine
        String name = reader.readLine();

        // Printing the read line
        System.out.println("Hello " + name + "!!!");
    }
}

BufferedReader takes a Reader as input. Here we are passing System.in to indicate receive input from the console. Method readline() reads the data from the buffer when the user presses the enter key. Below is the output from the program,

4.2 Reading from a file

In this example, I am going to show how you can read from a file line by line.

BufferedReaderFileRead.java

package com.jcg;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class BufferedReaderFileRead {
    public static void main(String[] args) throws IOException {
        //Enter data to BufferedReader from a file
        String line = null;
        System.out.println("Reading fom file");
        BufferedReader reader =
                new BufferedReader(new FileReader(System.getProperty("user.dir") + 
				"\\src\\com\\jcg\\test-file.txt"));

        // Reading data using readLine
        while ((line = reader.readLine()) != null) {
            // Printing the read line
            System.out.println(line);
        }
        System.out.println("Finished reading file");
    }
}

Here we are passing an instance of a FileReader. The while loop iterates till we reach end of the file. The output of the program is as below,

Both examples use default buffer size. If you would like to specify your own buffer size then use the other variety of constructor as below,

BufferedReader reader = new BufferedReader(System.in, 1024);

1024 is the size of buffer you are intending to use.

5. When to use BufferedReader

BufferedReader is a preferred choice when we have to read from a long stream of Strings. BufferedReader can read in chunks of data, it is efficient as compared to Scanner class.

BufferedReader is thread-safe. Hence it is suitable in the multi-threaded environment as compared to the Scanner.

As compared to Scanner, BufferedReader is fast and less CPU intensive.

6. Download the source code

For the demo program, I am using JDK11 and IntelliJ Idea IDE.

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