Syntax for command line arguments in Java - Mini Project: Build & Apply

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Syntax for command line arguments

📖 Scenario: You want to create a simple Java program that reads names from the command line when you run it. This is like telling your program some information before it starts, just like giving instructions to a friend before they begin a task.

🎯 Goal: Build a Java program that takes exactly two names as command line arguments and prints a greeting message using those names.

📋 What You'll Learn

Create a Java class named Greeting

Use the main method with String[] args to receive command line arguments

Access the first and second command line arguments using args[0] and args[1]

Print a greeting message combining both names

💡 Why This Matters

🌍 Real World

Many Java programs accept information from the command line to customize their behavior without changing the code. For example, tools, scripts, and utilities use command line arguments to know what files to process or what options to use.

💼 Career

Understanding command line arguments is important for Java developers because it helps in creating flexible programs and working with automation scripts, build tools, and deployment processes.

1

Create the Greeting class with main method

Write a public class called Greeting with a public static void main method that takes String[] args as parameter.

Java

public class Greeting {
    public static void main(String[] args) {
        // Your code here
    }
}

💡 Need a hint?

The main method is the entry point of a Java program. It must be public static void main(String[] args).

2

Add variables to store the first and second command line arguments

Inside the main method, create two String variables named firstName and secondName. Assign args[0] to firstName and args[1] to secondName.

Java

public class Greeting {
    public static void main(String[] args) {
        // Your code here
    }
}

💡 Need a hint?

Command line arguments are stored in the args array. The first argument is args[0], the second is args[1].

3

Create a greeting message using the two names

Inside the main method, create a String variable named message that combines firstName and secondName into the text: "Hello, <firstName> and <secondName>!" using string concatenation.

Java

public class Greeting {
    public static void main(String[] args) {
        String firstName = args[0];
        String secondName = args[1];
        // Your code here
    }
}

💡 Need a hint?

Use the + operator to join strings and variables into one message.

4

Print the greeting message

Use System.out.println to print the message variable inside the main method.

Java

public class Greeting {
    public static void main(String[] args) {
        String firstName = args[0];
        String secondName = args[1];
        String message = "Hello, " + firstName + " and " + secondName + "!";
        // Your code here
    }
}

💡 Need a hint?

Use System.out.println(message); to show the message on the screen.