Java Hello World!

This post demonstrates how to write a simple Java program.

1. create file end with .java

2. writes the following code

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

3. run javac filename.java to compile. If successful, a new file name filename.class will be created.

4. finally, run java filename to run the program.

Some elaboration:

• public is an access modifier indicating that the class and method can be accessed by others. static means it's a static method that is accessible without creating an instance of the class. void means the method doesn't return anything. main is the entry point for any Java program. When the program start, it looks for the main method and executes it. System.out.println() is a built-in method call. Hello World! is a string literal.
• Java can be considered as both interpreted and compiled language. It compiles the source code into .class files when you run javac, and JVM interprets the compiled code when you run java.