CODEWITHSUNDEEP
javalambdajava-8
aatuc210
aatuc210

Reputation: 1868

Transforming if-else to lambda expression

I'm trying to transform a simple if-else statement that I've found myself using all over the place to a more elegant lambda expression. But I'm having a hard time coming up with a solution from what I've been reading.

The simple statement goes like:

if (status.getStatus() == 'A') then
  handleA();
else if (status.getStatus() == 'B') then
  handleB();
else
  handleEverythingElse();

I know I could use the Command pattern with a map, but I'm sure there's some Java 8 elegance that I'm missing. Could someone show me the interface & impl, as well as it's usage in the body of the code (I learn by example)?

Any help would be much appreciated!

Upvotes: 0

Views: 563

Answers (2)

aatuc210
aatuc210

Reputation: 1868

Maybe I hadn't fully explained my problem, but my colleague proposed another solution that I really like. He suggested I make the if-else block a java.util.Supplier, and invoke it in the Entity class where I need it.

So my code went from this block of logic sprinkled everywhere:

public class ServiceImpl {
  ...
  if (entity.getStatus) == 'A' then
    finalStatus = handleA();
  else if (entity.getStatus() == 'B') then
    finalStatus = handleB();
  else
    finalStatus = handleEverythingElse();
  ...
}

To this nicely compacted form:

public class ServiceImpl {
  finalStatus = entity.getFinalStatus(this::handleStatus);

  public int handleStatus() {
    return dao.getStatus();
  }
}

With the implementation in my Entity class:

public class Entity {
  public int handleStatus(Supplier<Integer> s) {
    int finalStatus;
    if (status) == 'A' then
      finalStatus = handleA();
    else if (status() == 'B') then
      finalStatus = handleB();
    else
      finalStatus = supplier.get();
    return status;
  }
}

I hope this make sense...

Upvotes: 0

GhostCat
GhostCat

Reputation: 140457

If/else or even switch are not the "good OO design" answer. Neither are lambdas. Retrieving the status from somewhere, to make then a decision based on that - that is procedural programming; not OO.

You see, what you actually have in front of you - is a state machine. You have different states; and the point is: if your "thing" is in state A; then you want to do something ( invoke handleA() ). If your are in state B; you want to do something too ( like invoke handleB() ).

So, what you actually have is:

abstract class State {
  abstract void doIt();
...

StateA extends State {
  @Override
  void doIt() { handleA(); }

So, from the client side, you just call doIt() on same object of class State.

Thus: if you are really interested in improving your code base, learn how to use polymorphism to get rid of your if/else/switch statements.

You can watch this video to get an idea what I am talking about.

Upvotes: 2

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