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User Input and Display ⌨️

Prerequisites: Variables & Data Types

Mentor's Note: In Java, input is a bit more formal than in other languages. You need to "import" a special worker called the Scanner. 💡

🌟 The Scenario: The Customer Receipt 🧾

Imagine you are at a checkout counter.

  • The Logic: The clerk scans your item (Input). 📦
  • The Result: The total is printed on your receipt (Output). ✅

💻 Implementation: The Scanner Lab

// 🛒 Scenario: Greeting a Customer
// 🚀 Action: Using the Scanner class to read data

import java.util.Scanner; // 📦 1. Import the worker

public class GreetingLab {
    public static void main(String[] args) {
        // 📦 2. Create the Scanner object
        Scanner scanner = new Scanner(System.in);

        // --- Taking String Input (Text) 📛 ---
        System.out.print("Enter your name: ");
        String name = scanner.nextLine(); // Reads the whole line
        System.out.println("Hello, " + name + "!");

        // --- Taking Integer Input (Numbers) 🔢 ---
        System.out.print("Enter your age: ");
        int age = scanner.nextInt(); // Reads only the next integer
        System.out.println("You are " + age + " years old.");

        // 📦 3. Close the worker (Best Practice)
        scanner.close();
    }
}

📖 Key Concepts

  • Scanner: A powerful Java class used to read user input. You must import it first.
  • System.in: This tells the Scanner to "listen" to your keyboard.
  • nextLine(): Used for reading sentences (text).
  • nextInt(): Used for reading whole numbers.
  • close(): Always close your Scanner when finished to save computer resources.

🧠 Step-by-Step Logic

  1. Start 🏁
  2. Bring in the Scanner tool (import).
  3. Set up the Scanner to listen to the keyboard (new Scanner(System.in)).
  4. Prompt the user: "Enter your name: ".
  5. Store the user's typed text into a String variable.
  6. Display the message back.
  7. End 🏁

🎯 Practice Lab 🧪

Task: Calculator

Task: Ask the user for two numbers, add them together, and print the total. Hint: Use scanner.nextInt() twice and a sum variable. 💡

Quick Quiz

Quick Quiz

Which package must you import to use the Scanner class? - [ ] java.io - [ ] java.lang - [x] java.util - [ ] java.swing

Explanation: The Scanner class is located in the java.util (Utility) package.

📈 Learning Path