Read input from console in Java

This post will discuss how to read input from console in Java using Scanner, BufferedReader, and Console class. The input can be of different types, such as String, Integer, Double, Long, etc.

1. Using `Scanner` Class

The standard approach is to use the Scanner class in Java for reading input from the console, which splits the input into tokens using whitespace as a delimiter, which then can be conveniently converted into values of different types using the various next methods, as shown below:

import java.util.Scanner;

class Main

{

// Program to read input from console in Java using `Scanner`

public static void main(String[] args)

{

// Constructs a new `Scanner` instance to scan values from the input stream

Scanner scanner = new Scanner(System.in);

// read the whole line

System.out.println(scanner.nextLine());

// get the next double token

System.out.println(scanner.nextDouble());

// get the next string token

System.out.println(scanner.next());

// get the next integer token

System.out.println(scanner.nextInt());

// get the next long token

System.out.println(scanner.nextLong());

// close the scanner

scanner.close();

}

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2. Using `BufferedReader` Class

The problem with the Scanner class is that it is way too slow. We can also use the BufferedReader class in Java, which offers much better performance than the Scanner class. The whole line can be read as a string using the readLine() method and can be converted into values of different types using the utility methods provided by corresponding wrapper classes. For an integer, we can use the read() method.

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

class Main

{

// Program to read input from console in Java by using `BufferedReader`

public static void main(String[] args)

{

BufferedReader br = null;

try {

// Create a buffered character-input stream

br = new BufferedReader(new InputStreamReader(System.in));

// read the whole line

System.out.println(br.readLine());

// get double

System.out.println(Double.parseDouble(br.readLine()));

// get integer

System.out.println(br.read());

// close the stream

br.close();

} catch (IOException e) {

e.printStackTrace();

}

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3. Using `Console` Class

We can also use the Console class to access the character-based console device. To get the unique Console object associated with the current JVM, we can call the System.console() method.

import java.io.Console;

class Main

{

// Program to read input from console in Java by using `Console` class

// This will only work with the command line environment.

public static void main(String[] args)

{

Console console = System.console();

if (console != null)

{

// read the whole line

System.out.println(console.readLine());

// get double

System.out.println(Double.parseDouble(console.readLine()));

// get integer

System.out.println(Integer.parseInt(console.readLine()));

}

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That’s all about reading input from the console in Java.

Read input from console in Java

1. Using Scanner Class

2. Using BufferedReader Class

3. Using Console Class

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1. Using `Scanner` Class

2. Using `BufferedReader` Class

3. Using `Console` Class