Scanner – Taking User Input

Now that we know how to print messages, let’s learn how to ask the user for input!

➡️ Scanner is a special tool in Java that lets us take input from the keyboard.

1. Why Do We Need Scanner?

Imagine your Java program is like a robot that can talk.

• Right now, it can print messages (System.out.println(...)), but it can’t listen to you!
• With Scanner, we can make the robot ask questions and process answers.

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2. Importing Scanner (Bringing the Tool In)

Before using Scanner, we need to import it. Think of this like grabbing a notepad so the robot can take notes.

import java.util.Scanner;

• This tells Java that we want to use Scanner.
• Java already has Scanner built-in—we just need to bring it into our program.

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3. Creating a Scanner (Turning It On!)

To start using Scanner, we need to turn it on.

Scanner scanner = new Scanner(System.in);

• Scanner scanner → Creates a Scanner object (our robot’s "ears").
• new Scanner(System.in) → Tells it to listen for keyboard input.

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4. Taking User Input

Let’s ask for the user’s name and print it back!

import java.util.Scanner; // Step 1: Import Scanner

public class UserInput {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in); // Step 2: Create Scanner

        System.out.print("Enter your name: "); // Step 3: Ask for input
        String name = scanner.nextLine(); // Step 4: Capture what they type

        System.out.println("Hello, " + name + "!"); // Step 5: Use the input
    }
}

Example Interaction:

Enter your name: Alex  
Hello, Alex!

➡️ .nextLine() captures everything the user types and stores it in name.
➡️ The program prints a message using their name.

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5. Taking Different Types of Input

Scanner can take different types of input, not just text!

Data Type	Scanner Method	Example Input
String (text)	scanner.nextLine();	"Alex"
int (whole number)	scanner.nextInt();	25
double (decimal number)	scanner.nextDouble();	3.14

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6. Example: Asking for Name and Age

import java.util.Scanner;

public class UserInfo {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in); // Create Scanner

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

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

        System.out.println("Hello, " + name + "! You are " + age + " years old.");

        scanner.close(); // Close Scanner
    }
}

Example Interaction:

Enter your name: Emily  
Enter your age: 22  
Hello, Emily! You are 22 years old.

➡️ .nextInt() takes a whole number.
➡️ .nextLine() takes text.

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7. Closing the Scanner (Cleaning Up)

After using Scanner, we always close it to free up memory.

scanner.close();

Think of this like turning off the robot’s ears when we’re done talking.

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8. Summary of Scanner Methods

Method	What It Captures	Example Input
.nextLine()	A full sentence (String)	"Hello world"
.nextInt()	A whole number (int)	42
.nextDouble()	A decimal number (double)	3.14
.nextBoolean()	A true/false value	true