Initialize a new object from class in Enum

Question

I have an Enum called Plugins:

public enum Plugins {

    ROTATING_LINE (plugin.rotatingline.RotatingLine.class),
    SNOW_SYSTEM (plugin.snow.SnowSystem.class);

    private Class<?> c;

    private Plugins (Class<?> c) {
        this.c = c;
    }

    public Class<?> getClassObject() {
        return c;
    }

}

What I would like to do is to loop through all the enums in Plugins and create new objects from those using the variable c like this:

for (Plugins plugins : Plugins.values()) {
    Class<?> c = plugins.getClassObject();
    pluginList.add(new c(400, 400));
}

Is there a way of accomplishing this with a similar method? The reason why I want to do this is to create a list of classes that should be added to the List plugins when I start my application.

Answer 1

Since you are iterating over the plugins, I guess all plugins' constructors have the same number & type of parameters. (I do not understand your plugins.add(...) though.)

Anyways, if you want to use Enums, I would do the following, using constant-specific method implementations instead of type tokens/reflection:

public enum PluginTypes {
   ROTATING_LINE { Plugin create(int x, int y){
         return new plugin.rotatingline.RotatingLine(x,y);} },
   SNOW_SYSTEM { Plugin create(int x, int y){
         return new plugin.snow.SnowSystem(x,y);} };

   abstract Plugin create(int x, int y);
}

public interface Plugin {
  //...
}

Then your loop would look something like this:

List<Plugin> plugins = new ArrayList<Plugin>();

for (PluginTypes pt : PluginTypes.values()) {
    plugins.add(pt.create(400, 400));
}

On the other hand, if you know your implementation classes of Plugin anyways, why not use them directly instead of via the PluginTypes Enum?

Answer 2

Create an interface for the plugins

public interface Plugin{
     setShapeType();
     setX();
     setY();
     ...
  }

Create a method on the enum that creates an instance of Plugin.

public enum Plugins {

        ROTATING_LINE (plugin.rotatingline.RotatingLine.class),
        SNOW_SYSTEM (plugin.snow.SnowSystem.class);

        private Class<? extends Plugin> c;

        private Plugins (Class<? extends Plugin> c) {
            this.c = c;
        }

        // This acts as a constructor that takes args, I am assuming the args you need 
        public Class<? extends Plugin> createInstance(String shapeType,int x, int y) {
            Plugin plugin = c.newInstance();
            plugin.setShapeType(shapeType);
            plugin.setX(x);
            plugin.setY(y);
            return plugin;
        }

    }

Instantiate in loop

List<Plugin> myPlugins = new ArrayList<Plugin>();

for (Plugins plugins : Plugins.values()) {
    myPlugins.add(plugin.createInstance(Shaped.parent, 400, 400));
}

Please note this is Psuedo Code