Writing first Java program - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Java program?

Look at this Java program. What will it print when run?

Java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

A Hello, Java!

B hello, java!

C Hello Java

D Compilation error

💡 Hint

Check the exact text inside the quotes and capitalization.

The program prints exactly what is inside the quotes in System.out.println, including capitalization and punctuation.

🧠 Conceptual

intermediate

What is the role of the main method in a Java program?

In Java, what does the main method do?

A It stores all the variables used in the program.

B It automatically saves the program to a file.

C It is the starting point where the program begins execution.

D It defines the layout of the user interface.

💡 Hint

Think about what happens when you run a Java program.

The main method is where Java starts running the program. Without it, the program won't run.

🔧 Debug

advanced

What error does this Java program produce?

Look at this Java code. What error will it cause when compiled?

Java

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

A Syntax error: missing curly brace

B No error, prints Hello World

C Runtime error: NullPointerException

D Syntax error: missing semicolon

💡 Hint

Check the end of the System.out.println line.

Java statements must end with a semicolon. This line is missing it, causing a syntax error.

📝 Syntax

advanced

Which option correctly declares the main method in Java?

Choose the correct way to write the main method header in Java.

A static public void main(String args)

B public static void main(String[] args)

C public void static main(String args[])

D void public static main(String[] args)

💡 Hint

Remember the order and types in the method signature.

The correct order is public static void main(String[] args). Other orders or missing brackets cause errors.

🚀 Application

expert

How many lines will this Java program print?

Consider this Java program. How many lines will it print when run?

Java

public class CountLines {
    public static void main(String[] args) {
        for (int i = 0; i < 3; i++) {
            System.out.println("Line " + i);
        }
    }
}

A 3

B 4

C 0

D 1

💡 Hint

Count how many times the loop runs.

The loop runs from i=0 to i=2, printing one line each time, so 3 lines total.