OOPExampleToAvoidExternalDecisions.java

// here is an example of bad implementation that breaks encapsulation AND is hard to extend
class MyService {
   void doSomethingWith(MyInterface instance) {
     if(instance instanceof FirstImpl) {
       doSomething((FirstImpl) instance);
     } else if (instance instanceof SecondImpl) {
       doSomethingElse((SecondImpl) instance);
     } else {
       defaultBehaviour(instance);
     }
   }
}

// here is the same code but the decision 

interface MyInterface {
   // here we use a consumer interface but we can directly return values or do computations or return values directly.
   Consumer<MyInterface> somethingThatDoesSomething();
}

class FirstImpl implements MyInterface {
  Consumer<MyInterface> somethingThatDoesSomething() {
    return // ...
  }
}

class SecondImpl implements MyInterface {
  Consumer<MyInterface> somethingThatDoesSomething() {
    return // ...
  }
}

class DefaultImpl implements MyInterface {
  Consumer<MyInterface> c() {
    return // ...
  }
}

class MyService {
   void doSomethingWith(MyInterface instance) {
     instance.somethingThatDoesSomething().accept(instance);
   }
}

The second approach allows us to create new implementations of MyInterface without ever having to modify MyService.
So the point is to have a common interface that is used by all services AND WITHOUT exception have the parameter provide the "customized" implementation of its own type.