In this article, we discuss three different ways for reading input from the user in the command line environment (also known as the “console”). Each way is fairly easy to use and also has its own advantages and drawbacks.

 

1. Reading User's Input using BufferedReader class

By wrapping the System.in (standard input stream) in an InputStreamReader which is wrapped in a BufferedReader, we can read input from the user in the command line. Here’s an example:

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
System.out.print("Enter your name: ");

String name = reader.readLine();
System.out.println("Your name is: " + name);

In the above example, the readLine() method reads a line of text from the command line.

Advantages: The input is buffered for efficient reading.

Drawbacks: The wrapping code is hard to remember.

 

2. Reading User's Input using Scanner class

The main purpose of the Scanner class (available since Java 1.5) is to parse primitive types and strings using regular expressions, however it is also can be used to read input from the user in the command line. Here’s an example:

Scanner scanner = new Scanner(System.in);
System.out.print("Enter your nationality: ");
String nationality = scanner.nextLine();

System.out.print("Enter your age: ");
int age = scanner.nextInt();

Advantages:

• Convenient methods for parsing primitives (nextInt(), nextFloat(), …) from the tokenized input.
• Regular expressions can be used to find tokens.

Drawbacks:

• The reading methods are not synchronized.

Learn more: Java Scanner Tutorial and Code Examples

 

3. Reading User's Input using Console class

The Console class was introduced in Java 1.6, and it has been becoming a preferred way for reading user’s input from the command line. In addition, it can be used for reading password-like input without echoing the characters entered by the user; the format string syntax can also be used (like System.out.printf()). Here’s an example code snippet:

Console console = System.console();
if (console == null) {
	System.out.println("No console: non-interactive mode!");
	System.exit(0);
}

System.out.print("Enter your username: ");
String username = console.readLine();

System.out.print("Enter your password: ");
char[] password = console.readPassword();

String passport = console.readLine("Enter your %d (th) passport number: ", 2);

Advantages:

• Reading password without echoing the entered characters.
• Reading methods are synchronized.
• Format string syntax can be used.

Drawbacks:

• Does not work in non-interactive environment (such as in an IDE).

Learn more: Java Console Input Output Examples

 

4. Java Reading User's Input Example Program

For your convenient and reference purpose, we combine the above code snippet into a demo program whose source code looks like this:

package net.codejava.io;

import java.io.*;
import java.util.*;

public class UserInputConsoleDemo {

	public static void main(String[] args) {

		// using InputStreamReader
		try {
			BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));			
			System.out.print("Enter your name: ");

			String name = reader.readLine();
			System.out.println("Your name is: " + name);
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}

		// using Scanner
		Scanner scanner = new Scanner(System.in);
		System.out.print("Enter your nationality: ");
		String nationality = scanner.nextLine();
		System.out.println("Your nationality is: " + nationality);

		// using Console
		Console console = System.console();
		if (console == null) {
			System.out.println("No console: not in interactive mode!");
			System.exit(0);
		}

		System.out.print("Enter your username: ");
		String username = console.readLine();
		
		System.out.print("Enter your password: ");
		char[] password = console.readPassword();

		System.out.println("Thank you!");
		System.out.println("Your username is: " + username);
		System.out.println("Your password is: " + String.valueOf(password));

		// using Console with formatted prompt
		String job = console.readLine("Enter your job: ");
		
		String passport = console.readLine("Enter your %d (th) passport number: ", 2);

		System.out.println("Your job is: " + job);
		System.out.println("Your passport number is: " + passport);
	}	
}

 

Watch the video:

 

References:

• Console class Javadoc
• I/O from the Command Line - The Java Tutorials
• Scanner class Javadoc
• BufferedReader class Javadoc

 

Related Tutorials:

• Java Console Input Output Examples
• Java Scanner Tutorial and Code Examples

 

Other Java File IO Tutorials:

• How to Read and Write Text File in Java
• How to Read and Write Binary Files in Java
• Java IO - Common File and Directory Operations Examples
• Java Serialization Basic Example
• Understanding Java Externalization with Examples
• How to compress files in ZIP format in Java
• How to extract ZIP file in Java