Java Methods Container

Question

I'm trying to implement an action/reaction system in Java.
For that, I need to have all my methods stock in a container so I can easily call the response I need with the return of the action I want.
Being a C ++ developer and new to Java my first intuition was to create an array of function pointers (or at least reproduce it) so I tried to used anonymous subclasses. But didn't get the result I was looking for.
So I tried with lambdas, here is a sample of what I'm trying to do.

    public class Test {
      public Map<Integer, Vector<String>> actions = new HashMap<>();
      public Map<Integer, Integer> responses = new HashMap<>();

      public Test() {
        Vector<String> v= new Vector<String>();

        actions.put(0, action0());
        actions.put(1, action1());
        responses.put(0, response0(Vector<String>)); // How can I leave aside this argument which I don't know at this point ?
        responses.put(1, response1(Vector<String>));
      }

      public Vector<String> action0() {...}
      public Vector<String> action1() {...}

      // This methods takes actions return as argument
      public Integer response0 (Vector<String>) {...}
      public Integer response1 (Vector<String>) {...}

      public void run() {
        // When I run, I want to be able to launch any of my responses with any of my actions return
        responses.get(0) 
      }
   }

Am I at least trying a good way to solve this problem ?
Thanks a lot

I can't understand your question well. Do you want to do call "action" and with that return value call "response"? — SungJin Steve Yoo, Oct 29 '17 at 02:30
I don't want to stray off topic but, unless this approach is mandatory, you might want to look at `RxJava`. — ChiefTwoPencils, Oct 29 '17 at 02:30
...and since you're coming from C++ to Java, are you sure a [`Vector`](https://stackoverflow.com/questions/1386275/why-is-java-vector-class-considered-obsolete-or-deprecated) is what you want to use? — ChiefTwoPencils, Oct 29 '17 at 02:33
@SungJinSteveYoo Yes that's exactly what I want to do But I have tons of actions and responses that's why I'm trying to find an elegant and parameterized way to bind response to action — Gobind Willy, Oct 29 '17 at 02:34
as ChiefTwoPencils said, Java's `Vector` is different from C++'s `vector`. equivalent data structure is `ArrayList`. And also he is right, using `RxJava` will give you the implementation that you want — SungJin Steve Yoo, Oct 29 '17 at 02:35
I will say look at command pattern that even java swing adapts... i.e how you register an action listener to a component, and then when action is performed, you invoke your response code — Optional, Oct 29 '17 at 02:39
Well Thanks, gonna change from Vector to ArrayList, but my real issue is to find a way to stock all of my methods without creating multiple conditions to match actions and reponses — Gobind Willy, Oct 29 '17 at 02:40
plz update your `run()` method's code to clarify the behaviour that you want — SungJin Steve Yoo, Oct 29 '17 at 02:45
Yes, please update your code. You have inconsistencies that apparently require a few assumptions. — ChiefTwoPencils, Oct 29 '17 at 02:49

Andreas · Accepted Answer · 2017-10-29T13:40:16.777

~~Your code has a few flaws, so I'll assume that getHashtag() and action1() were supposed to be the same, and similar for the other three.~~

~~Also, I'll assume that the second responses.put() should have been key 1, not 0.~~ Also, the parameter to your responseX() methods need a name.

Anyway, you need a functional interface, so you can give the responseX() methods as Method References.

In your case, the responseX() methods take a Vector<String> as parameter, and returns an Integer, so the functional interface would be Function<Vector<String>, Integer>.

You can then build a map of those methods, to be executed later.

public Test() {
    // Here we can build map of response methods first, if we like, even though Vectors don't exist yet
    Map<Integer, Function<Vector<String>, Integer>> responseMethods = new HashMap<>();
    responseMethods.put(0, this::response0);
    responseMethods.put(1, this::response1);

    // Now we build the action map of Vectors
    Map<Integer, Vector<String>> actions = new HashMap<>();
    actions.put(0, action0());
    actions.put(1, action1());

    // At this time, we can now execute the referenced methods to get the actual responses
    Map<Integer, Integer> responses = new HashMap<>();
    for (Integer key : actions.keySet()) {
        Vector<String> v = actions.get(key);
        Function<Vector<String>, Integer> responseMethod = responseMethods.get(key);
        Integer response = responseMethod.apply(v);
        responses.put(key, response);
    }
}

public Vector<String> action0() {...}
public Vector<String> action1() {...}

public Integer response0(Vector<String> v) {...}
public Integer response1(Vector<String> v) {...}

You can even defer the execution of the action methods if you want:

public Test() {
    // Here we can build map of response methods first, if we like, even though Vectors don't exist yet
    Map<Integer, Function<Vector<String>, Integer>> responseMethods = new HashMap<>();
    responseMethods.put(0, this::response0);
    responseMethods.put(1, this::response1);

    // Now we build the action map of Vectors
    Map<Integer, Supplier<Vector<String>>> actionMethods = new HashMap<>();
    actionMethods.put(0, this::action0);
    actionMethods.put(1, this::action1);

    // At this time, we can now execute the referenced methods to get the actual responses
    Map<Integer, Integer> responses = new HashMap<>();
    for (Integer key : actionMethods.keySet()) {
        Supplier<Vector<String>> actionMethod = actionMethods.get(key);
        Function<Vector<String>, Integer> responseMethod = responseMethods.get(key);
        Vector<String> v = actionMethod.get();
        Integer response = responseMethod.apply(v);
        responses.put(key, response);
    }
}

Java Methods Container

1 Answers1