using Optional to validate null when getting value from map

Question

I have this line

List<Integer> someListWithLongName = someMapWithLongName.containsKey(someObjectWithLongName.get()) 
    ? someMapWithLongName.get(someObjectWithLongName.get()) 
    : Collections.emptyList();

That I wanted to change to make it a bit more readable, so I chose:

List<Integer> someListWithLongName = Optional.of(someMapWithLongName.get(someObjectWithLongName.get())
    .orElse(Collections.emptyList())

But I was told that the purpose of Optional is different. However, I'm failing to see why.
Is it really so? why?

https://docs.oracle.com/javase/8/docs/api/java/util/Map.html#getOrDefault-java.lang.Object-V- — JB Nizet, Oct 25 '18 at 20:36

score 3 · Accepted Answer · answered Dec 04 '18 at 01:58

Some people will have different views on this but a good practice is to always use something the way it was intended.

see this answer for consequences of misusing the Optional<T> type.

instead of your current solution, a better solution hinted by @JB Nizet would be using Map::getOrDefault available as of JDK8.

List<Integer> result = map.getOrDefault(key, Collections.emptyList());

using Optional to validate null when getting value from map

1 Answers1