using object functions in java

Question

I'm trying to implement function objects in Java. I have a Unit class, with a default addition function that should be used in most initializations of a Unit object. However, for some issues, I need a different addition function. The code will look something like this:

public class Unit() {
   public Unit(unitType) {
      if (unitType == "specialType") {
         additionFunc = defaultFunc } else {
         additionFunc = specialFunc }
      }
   }
   public int swim() {
      return additionFunc()
   }
  // definiion of regularFunc
  // definition of specialFunc

}

Then, from the main file:

Unit fish = new Unit(regularTyoe);
Unit fatFish = new Unit(specialType);
fish.swim(); //regular function is called
fatFish.swim(); //special function is called

That's it.. does anyone know how this can be done?

Answer 1

You need to look up inheritance and method overriding. It would probably help to read up on proper Object Oriented Programming as well.

The proper way to do this is:

class Fish {
  public void swim() {
    // normal swim
  }
}

class FatFish extends Fish {
  @Override
  public void swim() {
    // special swim
  }
}

Fish fish = new Fish()
Fish fatFish = new FatFish()
fish.swim()    // normal swim
fatFish.swim() // slow swim