Why Is That?

When writing the main method in Java, we write it with public static void main as shown below.

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

Why does it have this structure? Examining each part:

public

public is called an access specifier or access modifier. Among access specifiers, public means it can be used anywhere without restrictions. Conversely, there are protected which can only be used in inherited classes and private which cannot be accessed externally.

static

It means static. When attached to a method, it indicates that this method is a static method. When declared as static, it’s defined at the time Java is compiled. And it’s impossible to call static elements from non-static elements.

Especially, elements like the main method that serve as program entry points must be static because they need to perform work without creating objects.

void

It’s the return type of the method. void means there’s nothing to return. It simply returns to the calling location when the method ends.

main

It’s the method name. Just as there’s a main function in C language, Java also has one. It executes first when the program starts.

String[] args

It represents method parameters. It’s a String type array named args. As shown below, when executing Java through the command line, you can pass parameters.

java test.class test1 test2

Summary

Just like C language, the main method executes first in Java language. However, to execute, it must be loaded into memory in advance. Therefore, static is declared to make it usable without memory allocation (new). Especially, since the main method is called by the Java Virtual Machine (JVM), it must be declared as static and pre-loaded.