Why is it mandatory to implement "public Static void main (String [] args)"?

Question

Why it is mandatory to implement this method in a Java application?

Answer 1

It’s mandatory because every app needs a point of entry. Normally the operating system needs to know where the code starts, in Java it is actually its operating environment, it is the JRE that will start the application and needs to know what to call first. it was agreed that this method would be called main(), since other languages used something like this.

In fact you also need to specify which class will be the main one since the method main() may exist in other classes.

The body can be as simple as just calling another method. I see no use in it, except for some very specific purpose, other people do without knowing why.

It is not always mandatory

There are some situations where it is not required. It is the case of web applications that already start somewhere else from the framework used and then go calling what you programmed. In practice there is a main(), but not in your code.

It is also possible to function with only one static method within a class considered to be the main one. Nor do I see a general advantage in that, but it is possible according to a response in the OS.

class JavaAppWithoutMain {
    static {
        System.out.println("Hello World!");
    }
}

I put in the Github for future reference.

Signing

In the signature of the method was agreed to the use of String[] args to receive command line arguments - as they can be multiple and can contain any type of information the ideal would be a array of string. It has also been decided to return nothing to the operating system, unlike other languages that do. You can ignore this variable.

Unlike other Java languages it preferred not to give options and this is the only possible signature. The philosophy of language is to simplify, although it is debatable whether this is actually a simplification.

There are more details about each component in What public Static void main(String[] args means)?.

Answer 2

Generally, in any programming languages, this parameter represents the input data that will be passed to your program.

I don’t have much understanding about Java, although I have already tested it, and I know how it works.

If you for example have a class called Hello who has this String args[] as parameters, when you execute the command java Hello world

The result of this String args[] will be ["Hello", "world"].

I do not know if in all languages are like this, but in all that I have worked until today (Python, PHP and the like), the first argument that is the name of the program (in my example is "Hello") is always present.

This is very useful for you to pass arguments to your application.

Answer 3

Basically this method means that at you are making the class you are implementing the main.

It is he who makes the execution of all the code you build or calls-Ló.