Khalid Ahmad Khattak

Lesson 5 – User Input

In Java, user input is handled using a class called Scanner. Scanner allows you to read text, numbers, and other types of input from the keyboard.

1. Importing Scanner

Before using Scanner, you must import it:

import java.util.Scanner;

Then create a Scanner object:

Scanner input = new Scanner(System.in);

2. Reading a String

Example 1 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Enter your name: ");
        String name = input.nextLine();

        System.out.println("Hello " + name);
    }
}
        

3. Reading an Integer

Example 2 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

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

        System.out.println("You are " + age + " years old.");
    }
}
        

4. Reading a Decimal Number (double)

Example 3 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Enter a number: ");
        double num = input.nextDouble();

        System.out.println("You entered: " + num);
    }
}
        

5. Reading Multiple Values

Example 4 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Enter first number: ");
        int x = input.nextInt();

        System.out.print("Enter second number: ");
        int y = input.nextInt();

        int sum = x + y;

        System.out.println("Sum = " + sum);
    }
}
        

6. Reading Text After Numbers

After reading numbers with nextInt() or nextDouble(), you must clear the buffer using nextLine().

Example 5 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Enter age: ");
        int age = input.nextInt();
        input.nextLine(); // clear input buffer

        System.out.print("Enter your city: ");
        String city = input.nextLine();

        System.out.println("Age: " + age);
        System.out.println("City: " + city);
    }
}
        

7. Boolean Input

Example 6 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Is Java fun? (true/false): ");
        boolean answer = input.nextBoolean();

        System.out.println("Your answer: " + answer);
    }
}
        

8. Real-Life Example: Simple Login

Example 7 – Full Program

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.print("Enter username: ");
        String username = input.nextLine();

        System.out.print("Enter password: ");
        String password = input.nextLine();

        System.out.println("Login successful!");
        System.out.println("Welcome " + username);
    }
}
        

9. Summary

• Use Scanner to read keyboard input
• Use nextLine() for text
• Use nextInt(), nextDouble(), etc., for numbers
• Always clear buffer when mixing numbers and text

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