Statement about main:
1.java virtual machine call, so it must be public;

2. When there is a main() method in a class, executing the command "java class name" will start the virtual machine to execute the main method in the class.

Since the JVM is running the Java application, the main method is called first. The object of this class is not instantiated when called, but is called directly by the class name, so it needs to be restricted to public static. (class name. main())

3. jvm has a limit, there can be no return value, so the return value type is void; (it seems that because you can't get the return value, you just don't want it)

4. The main function can only appear in the public class, which is the public class.

In addition to this, args[] in the main method is used for what, I have been curious before. Later, I found out that the information was known:

The string parameter array in the main() method is used to receive command line input parameters. The parameters of the command line are separated by spaces.

The parameter args provides a means for the program user to interact with the program in the command line state.

For example: javac Test1.java

           java Test1  60 50 40

Next iterate over the args[] array,

for(int i=0;i<args.length;i++){ 

            System.out.println(args[i]); 
        } 

The result is 60 50 40

There is another question: Why is the parameter passed in Application.launch() in Javafx args?

I encountered this when I first learned javafx:

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

In fact, the purpose of this biography is

Used to pass arguments from the console, just like the main function main(String[] args), args is the argument passed by the console.

Sometimes you need to pass this parameter when you start it, such as executing the command in the console java Demo abc

, abc will be passed to the main function as a parameter args.

We know that passing an array name is actually a pass address. Application.launch() in Javafx is static

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

Then there is a problem, we often use eclipse or idea tools to write java programs and then run, instead of javac java such dos window form, then how to pass parameters to the args array.

In eclipse, you can select the running parameters at runtime: Click Run -> Run Configurations -> Java Application, then select the class corresponding to the project Test1, then click Arguments, enter the string "60 50 40" as the program in the program arguments box. Parameters, then click Apply -> Run