Function pointers/delegates in Java?

Question

For my Java game server I send the Action ID of the packet which basically tells the server what the packet is for. I want to map each Action ID (an integer) to a function.

Answer 1

You can use things in java.util.function (For Java 8+) to store a function. java.util.function docs

You have to go through this list and pick an appropriate function-class to use. I'll be using BiConsumer, which says:

Takes two inputs. Returns no result. Operates through side effects.

import java.util.function.BiConsumer;
import java.util.HashMap;
import java.util.Map;

public void init(){
  //>
  Map> actionMap = new HashMap<>();
  actionMap.put(123, this::someMethod);

  //note (optional): check key first: map.containsKey(someActionId)
  //call someMethod("argument1", "argument2")
  actionMap.get(123).accept("argument1", "argument2");
}

public void someMethod(String a, String b){
  //do something here
}