Reading from Standard Input

This lesson covers receiving standard input in Java using Scanner, so you can build a program that processes user input. It's for anyone searching "Java Scanner usage."

The Scanner class lets you receive input (standard input) from a keyboard or similar source. Use it when you want a command-line tool to prompt the user for something.

The example creates a Scanner with new Scanner(System.in), reads one line of input into name with scanner.nextLine(), and uses it in a greeting. Notice System.in represents keyboard input.

A common early mistake is choosing the wrong method for the type of input you're reading. You need to pick the right method — nextInt(), nextLine(), and so on — based on the input's type; mixing them can produce unexpected behavior.

In real projects, using an input value without validating it first can lead to unexpected errors, so combining it with a validation step is safer.

📖 Reference code

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter your name: ");
        String name = scanner.nextLine();
        System.out.println("Hello, " + name + "!");
    }
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Java directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).