Reading Input with Scanner

Make your program interactive

So far our programs only talk. To listen to the user, Java gives us the Scanner class. It reads what the user types in the terminal.

Scanner lives in a toolbox called java.util, so first we import it at the top of the file. To import something means to tell Java "I want to use this ready-made tool from elsewhere" — it is like fetching a tool from a shared cupboard before you start, so you can call it by its short name (Scanner) instead of its long full name.

import java.util.Scanner;

public class Greet {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("What is your name? ");
        String name = input.nextLine();

        System.out.print("How old are you? ");
        int age = input.nextInt();

        System.out.println("Hi " + name + "! Next year you will be " + (age + 1) + ".");
    }
}

The reading-input flow, step by step

Every interactive program follows the same five steps in order. Here is exactly what the program above did:

1. Import the Scanner tool at the top: import java.util.Scanner;. Do this once, before the class.
2. Create a Scanner connected to the keyboard: Scanner input = new Scanner(System.in);. System.in means "input typed in the terminal".
3. Ask a question with System.out.print(...) so the user knows what to type.
4. Read their answer with the matching method — nextLine() for text, nextInt() for a whole number — and store it in a variable.
5. Use the stored value: print it back, do maths with it (like age + 1), or make a decision from it.

The Scanner methods you will use most