Java Runtime Input Explained args & Scanner Class

Core Java Beginner Crash Course – Session 4

Welcome to Session 4 of the Core Java Beginner Crash Course by Madras Academy! 🚀

In this session, we’ll explore runtime input in Java, an essential concept for building interactive applications. You’ll learn how to take user input dynamically using command-line arguments (args) and the Scanner class.

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📌 What You Will Learn

✅ Understanding the args variable in Java
✅ How to use command-line arguments
✅ Taking user input with the Scanner class
✅ Hands-on coding examples for better understanding

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📝 Understanding the ‘args’ Variable (Command-Line Arguments)

When executing a Java program, you can pass values directly from the command line using command-line arguments.

Example: Using Command-Line Arguments

javaCopyEditpublic class CommandLineExample {
    public static void main(String[] args) {
        if (args.length > 0) {
            System.out.println("You entered: " + args[0]);
        } else {
            System.out.println("No command-line argument provided.");
        }
    }
}

Execution:

shCopyEditjava CommandLineExample Hello

Output:

yamlCopyEditYou entered: Hello

Here, Hello is passed as an argument while running the program.

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🔍 Using Scanner Class for User Input

The Scanner class allows users to enter input at runtime.

Example: Using Scanner for User Input

javaCopyEditimport java.util.Scanner;

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

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

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

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

        scanner.close();
    }
}

Explanation:

• scanner.nextLine() reads a full line of text.
• scanner.nextInt() reads an integer input.
• .close() is used to release resources after input is taken.

Sample Output:

yamlCopyEditEnter your name: John
Enter your age: 25
Hello, John! You are 25 years old.

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🚀 Why Should You Learn Runtime Input Handling?

✔ Allows dynamic user interaction in Java programs
✔ Essential for taking input in console-based applications
✔ Helps in data processing and interactive application development

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