Inheritance of the main method

Question

I want to define a base class that defines the main method that instantiates the class and runs the method. However, there are a couple of problems. Here is the base class:

public abstract class Strategy
{
    abstract void execute(SoccerRobot robot);

    public static void main(String args)
    {
        Strategy s = new /*Not sure what to put here*/();
        s.execute(new SoccerRobot())
    }
}

And here is an example of a derived class:

public class UselessStrategy
{
    void execute(SoccerRobot robot)
    {
        System.out.println("I'm useless")
    }
}

It defines a simple execute method that should be called in the main method when used as the main application. However, for this I need to create an instance of the derived class from the main method of the base class. This is not possible.

I would prefer not to repeat the main method for each derived class, as it feels somewhat unobvious.

Is there a proper way to do this?

Answer 1

.
( )
Launcher ( )

public class Launcher
{
    public static void main(String args)
    {
       Strategy s = new UselessStrategy();
          //OR Strategy s = CreateInstance(args[0]) ;
          //OR equiv mechanism for Dependency Injection if you don't want to hardcode the derived strategy to use.
        s.execute(new SoccerRobot())
    }
}

Answer 2

, "main", , . :

public static void main(String args) throws Exception
{
  String className = (args.length > 0) ? args[0] : 'UselessStrategy';
  Strategy s = (Strategy) Class.forName(className).newInstance();
  s.execute(new SoccerRobot())
}

Class.forName , Andreas_D:

private static Map<String, Class<? extends Strategy>> STRATEGY_NAME =
    new HashMap<String, Class<? extends Strategy>>();

static {
    STRATEGY_NAME.put("Useless", UselessStrategy.class);
    STRATEGY_NAME.put("Better", BetterStrategy.class);
}

public static void main(String args[]) throws Exception {
    String className = (args.length > 0) ? args[0] : null;
    Class<? extends Strategy> klass = STRATEGY_NAME.get(className);
    if (klass == null) klass = UselessStrategy.class;
    Strategy s = klass.newInstance();
    s.execute();
}

, , .

Answer 3

.

public abstract class Strategy
{
    protected static Class<? extends Strategy> instanceClass;

    abstract void execute(SoccerRobot robot);

    public static void main(String args)
    {
        Strategy s = instanceClass.newInstance()
        s.execute(new SoccerRobot())
    }
}

public class UselessStrategy extends Strategy
{
    static {
        instanceClass = UselessStrategy.class;
    }

    void execute(SoccerRobot robot)
    {
        System.out.println("I'm useless")
    }
}

Answer 4

, .

public class UselessStrategy

do

Strategy s = new UselessStrategy();

Answer 5

.

, , , . main() .

.

Answer 6

? , , , execute.