Collections.emptyList() instead of null check?
If I have a rarely used collection in some class which may be instantiated many times, I may sometimes resort to the following \"idiom\" in order to save unnecessary object crea
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in order to save unnecessary object creations
That's a really bad idea which will litter your code with
== nullchecks and other handling of corner cases (and presumably end up in null pointer exceptions anyway)!Now I was wondering if I couldn't eliminate those null checks using
Collections.emptyList()No, not really.
emptyList()returns an empty list. You could doif (list.equals(Collections.but that will still throw a NullPointerException if
list == null, so it's still not what you're after.My recommendation: Always initialize the list to
new ArrayList, or, if you for instance want to return an empty list from a method, useCollections.emptyList()instead. (This returns the same instance every time, so no unnecessary object creation there either.)And then use
.isEmpty()to check if a collection is empty or not.
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