Writing first Java program - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the basic structure of a Java program?

A Java program has a class with a <code>main</code> method inside. The <code>main</code> method is where the program starts running.

beginner

What does System.out.println() do in Java?

It prints text or values to the screen and moves to the next line, so you can see output from your program.

beginner

Why do we need the public static void main(String[] args) method?

This method is the entry point of any Java program. The computer looks for it to start running your code.

beginner

What is a class in Java?

A class is like a blueprint or a container that holds code. Every Java program needs at least one class.

beginner

How do you save and run a Java program?

Save the file with a .java extension and the same name as the class. Then use javac to compile and java to run it.

What keyword starts the main method in a Java program?

A public

B start

C begin

D main

The main method starts with the keyword public to make it accessible.

Which method prints text to the console in Java?

A System.out.print()

B print()

C System.out.println()

D console.log()

System.out.println() prints text and moves to a new line.

What file extension should a Java source file have?

A .exe

B .java

C .class

D .txt

Java source files must be saved with the .java extension.

What is the name of the method where Java starts running your program?

A main()

B run()

C start()

D init()

Java looks for the main() method to begin execution.

Which command compiles a Java program?

A runjava

B java

C compile

D javac

Use javac to compile Java source code into bytecode.

Explain the role of the main method in a Java program.

Think about where the computer looks first to run your code.

Describe the steps to write, save, compile, and run a simple Java program.

Consider the full process from typing code to seeing output.