Java Hello World#

Note

Print “Hello World” using Java.

Installation#

  1. Download and install IntelliJ IDEA (one Java IDE).

  2. Use IntelliJ to create a new command line Java project, remember to select and download JDK (Java Development Kit, this tutorial have been written for JDK 8).

Classes and Methods#

Once the new project is created, IntelliJ will automatically create a file named Main.java:

public class Main {

    public static void main(String[] args) {
	// write your code here
    }
}

Here Main is a class and main is a method (function). In Java:

  • A method must be contained in a class

  • Class YourClassName should be contained in a file named YourClassName.java

  • main method is the entry point of our program

Next briefly explain keywords public and static:

  • public: accessible from other parts of the program

  • static: main method must be static

Basic structure of classes#

Keywords class ClassName {
    ...
}

Basic structure of methods#

Keywords ReturnType functionName(Parameters) {
    ...
}

Hello World#

Use System.out.println to print a String:

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

Click the Run buttom in IntelliJ, our first Java program will be executed.