Command line execution in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Java program with command line arguments

What is the output of this Java program when run with arguments hello world?

Java

public class Main {
    public static void main(String[] args) {
        System.out.println(args.length);
        for (String arg : args) {
            System.out.print(arg + " ");
        }
    }
}

A

0

B

1
hello world 

C

2
hello
world

D

2
hello world 

💡 Hint

Remember that command line arguments are passed as an array of strings to main.

The program prints the number of arguments, which is 2, then prints each argument separated by a space.

🧠 Conceptual

intermediate

Understanding Java command line argument indexing

If a Java program is run with the command java Program one two three, what is the value of args[1] inside main?

A IndexOutOfBoundsException

B "two"

C "three"

D "one"

💡 Hint

Array indexing in Java starts at zero.

args[0] is "one", args[1] is "two", args[2] is "three".

🔧 Debug

advanced

Identify the error when running Java program with no arguments

What error occurs when running this Java program with no command line arguments?

Java

public class Test {
    public static void main(String[] args) {
        System.out.println(args[0]);
    }
}

A NoSuchElementException

B NullPointerException

C ArrayIndexOutOfBoundsException

D Compilation error

💡 Hint

Accessing an array element that does not exist causes an exception.

args is an empty array when no arguments are passed, so args[0] access throws ArrayIndexOutOfBoundsException.

📝 Syntax

advanced

Correct command to compile and run Java program with arguments

Which command correctly compiles and runs a Java program named App.java with command line arguments foo bar?

A javac App.java && java App foo bar

B java App.java foo bar

C javac App.java foo bar && java App

D java App foo bar && javac App.java

💡 Hint

Remember that javac compiles and java runs the class without the .java extension.

Option A compiles first, then runs the class with arguments. Others misuse commands or order.

🚀 Application

expert

Determine output of Java program processing command line arguments

What is the output of this Java program when run with arguments 3 5 2?

Java

public class SumArgs {
    public static void main(String[] args) {
        int sum = 0;
        for (String arg : args) {
            sum += Integer.parseInt(arg);
        }
        System.out.println(sum);
    }
}

A 10

B 352

C 0

D NumberFormatException

💡 Hint

The program converts each argument to a number and adds them.

3 + 5 + 2 equals 10, so the program prints 10.