main Can methods be overloaded ？

• main Can methods be called by other methods ？
• main Can methods inherit ？

# Ali on both sides ：main Can methods inherit ？

yesterday , A netizen in wechat group , I posted the process of interviewing Ali in the group . One of the interviews , He's in the group PUA Other netizens . This interview question is ：Java Medium main Can methods inherit ？

We started to learn Java When it comes to programming , The first piece of code to run must be main Method ,main The format of the method is as follows ：

public static void main(String[] args) {


}

that main What's special about the method ？ Today, let's take a brief look at .

First, for main Method format definition ：

「public」 ：main The method is to start by JVM Loading ,public Is the highest accessible , So it needs to be declared as public;

「static」 ： Method is called either through an object , Or through classes , and main Method, because it is called by the virtual machine , So there is no need to generate objects , Then declare as static that will do ;

「main」 ： As for why the method name is main, I think it should refer to C The method name of the language ;

「void」 ：main Method exit , There is no need to have a relevant return value , So it is void;

「String[]」 ： This string array is used to accept user input parameters at runtime ; Because the string is in Java Is universal in , So using strings is the best choice ; Array words , Because we have more than one parameter , So the array must be appropriate ;

But from JDK1.5 After introducing dynamic parameters ,String[] Arrays can also be used String... args To achieve .

public static void main(String... args){
}

Except for the above JVM That's the rule main In addition to the special method , Other main Methods are no different from ordinary static methods .

# main Can methods be overloaded ？

This is OK , For example, we overload it with a method ：

public class Main {
    public static void main(String args) {
        System.out.println("hello world:" + args);
    }




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

Compile operation , Obviously there's no problem , except JVM Specified as an application entry main Out of the way , Other main Methods are more common methods .

# main Can methods be called by other methods ？

public class Main {
    private static int times = 3;




    public static void main2(String[] args) {
        times--;
        main(args);
    }




    public static void main(String[] args) {
        System.out.println("main Method execution :" + times);
        if (times <= 0) {
            System.exit(0);
        }
        main2(args);
    }
}

Run the code , You can find that the code can execute normally ：

main Method execution :3
main Method execution :2
main Method execution :1
main Method execution :0

So even as an application entry main Method , It can also be called by other methods , But pay attention to the closing mode of the program , Don't fall into a dead circle .

# main Can methods inherit ？

We've known before , When subclasses inherit , Subclasses can inherit the methods and variables of the parent class , So when the parent class defines main Method , And subclasses don't main The method is , That can inherit the parent class main Method , So as to run the program normally ？

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

Defining subclasses ：

public class Main2 extends Main {
}

At this time, we run subclasses Main2, You can find , Also printed hello world, This explanation main Methods can also be inherited . Then there is another hidden situation, which is also obvious , Human beings define their own main Method , Hide the implementation in the parent class , Then it's ok .

public class Main2 extends Main {
    public static void main(String [] args) {
        System.out.println("hello world Main2");
    }
}

At this time, you will print out your own content ：hello world Main2.

Look at it this way , except main Method is special as the entrance of application , In other cases, it is no different from the normal static method .