用于独立执行并作为jar库的Java应用程序

Question

I want to create a java application that can be executed in two ways. As a standard stand alone application, using main(args[]), and with in any java application using a jar, imported to that other application as an external library.

The problem i am facing is that i want to use the same function on both cases. This is causing be error, since i have to declare static the methods and variables when executed as stand alone application but as not static when i need to access it from an other application.

I have never done that before, so i am not 100% sure that this is a real problem. my past projects were always static all the way. I am guessing i could bread my code in two classes, having the main on one and every other method on the other and use it as it was a separate project. Is this a correct approach?

Answer 1

Try writing it like this:

public class DoubleDuty {
    // This is the main method executed using java -jar
    public static void main(String [] args) {
        DoubleDuty dd = new DoubleDuty();
        dd.complexApplication();
    }

    public void complexApplication() {
        // This can be executed by others who import this JAR.
    }
}

Answer 2

only one public static main() is necessary in you new class.

The main is always static, but you class can have instances.

You can call it by another class:

public class Class1 {
public static void main(String args[])
    {
    System.out.println("Class1 BEGINS !");
    }
}

public class Class2 {
    public static void main(String args[])
        {
        Class1.main(args);
        // or that
        Class1.main(new String[0]); beware if inside main , you read args !
        }

}

when you compile your jar as standalone, set the start to the other class: Lauch Configuration => set Class1 or Class2