Structure of a Java Program

1) Class

All Java code must live inside a class. Think of a class as the container (or blueprint) for your program.

class Hello {
}

The file name must match the public class name exactly. If the class is Hello, save the file as Hello.java.

2) The main Method

The JVM (Java Virtual Machine) looks for a specific method to start your program: public static void main(String[] args).

public static void main(String[] args) {
}

3) Curly Braces { }

Curly braces group code blocks:

• One pair for the class
• One pair for the main method

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

Every opening brace { must have a matching closing brace }.

Full Minimal Example

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