Key Concepts

Review core concepts you need to learn to master this subject

Classes

main() Method

Print Line

Comments

Whitespace

Compiling Java

Statements

Classes

public class Person {
  
  public static void main(String[] args) {
    
    System.out.println("I am a person, not a computer.");
    
  }
  
}

A class represents a single concept.

A Java program must have one class whose name is the same as the program filename.

In the example, the Person class must be declared in a program file named Person.java.

Hello World
Lesson 1 of 1
  1. 1
    Introduction to Java
    Welcome to the world of Java programming! Programming languages enable humans to write instructions that a computer can perform. With precise instructions, computers coordinate applications and sy…
    Start
  2. 2
    Hello Java File!
    Java runs on different platforms, but programmers write it the same way. Let’s explore some rules for writing Java. In the last exercise, we saw the file HelloWorld.java. Java files have a **….
    Start
  3. 3
    Print Statements
    Let’s take a closer look at this instruction from our previous program: System.out.println(“Hello World”); Print statements output information to the screen (also referred to as the output termin…
    Start
  4. 4
    Commenting Code
    Writing code is an exciting process of instructing the computer to complete fantastic tasks. Code is also read by people, and we want our intentions to be clear to humans just like we want our in…
    Start
  5. 5
    Semicolons and Whitespace
    As we saw with comments, reading code is just as important as writing code. We should write code that is easy for other people to read. Those people can be co-workers, friends, or even yourself! …
    Start
  6. 6
    Compilation: Catching Errors
    Java is a compiled programming language, meaning the code we write in a .java file is transformed into byte code by a compiler before it is executed by the Java Virtual Machine on your comp…
    Start
  7. 7
    Compilation: Creating Executables
    Compilation helped us catch an error. Now that we’ve corrected the file, let’s walk through a successful compilation. As a reminder, we can compile a .java file from the terminal with the comm…
    Start
  8. 8
    Java Review: Putting It All Together
    In this lesson, we’ve started writing our first programs in Java. We’ve also learned rules and guidelines for how to write Java programs: * Java programs have at least one class and one main() me…
    Start

What you'll create

Portfolio projects that showcase your new skills

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How you'll master it

Stress-test your knowledge with quizzes that help commit syntax to memory

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