How does Java run without a main function?

In Java, every program needs an entry point, which is typically the main method that serves as the program’s starting function. However, in some cases, if you want to run a Java program without a main method, you can consider using one of the following methods:

Using a static code block: In Java classes, a static code block can be used to implement the entry logic of a program. The static code block is executed when the class is loaded, and can be used to initialize variables, load resources, and perform other operations. For example:

public class MainWithoutMain {
    static {
        System.out.println("This is the entry point of the program");
        // Add your program logic here
    }

    public static void main(String[] args) {
        // This method can be empty or not used
    }
}

By using a launcher class, you can create a separate class containing a main method, and then call the code of other classes within that method. This method is similar to delegating the launch logic to another class. For example:

public class AppLauncher {
    public static void main(String[] args) {
        System.out.println("This is the entry point of the program");
        // Call other classes or methods here
    }
}

Using frameworks or tools: Some frameworks or tools offer custom program entry points, allowing you to run the program without a main method. For example, the Spring framework allows you to define the application context and specify custom startup logic.

Although Java programs typically use the main method as the entry point function, the above method can assist you in implementing entry logic in some special cases. Please choose the method that best suits your needs.