What does "(o==null ? a==null : o.equals(a))" mean in Java?

Question

What does "(o==null ? a==null : o.equals(a))" mean in Java? I'm reading this from the "contains" method documentation of an ArrayList.

https://www.baeldung.com/java-ternary-operator – luk2302 Jul 09 '22 at 09:55 — luk2302, Jul 09 '22 at 09:55
actually it is `nullsafe equals` – Andrey B. Panfilov Jul 09 '22 at 14:17 — Andrey B. Panfilov, Jul 09 '22 at 14:17

score 1 · Answer 1 · answered Jul 09 '22 at 09:54

1

It's ternary comparison, and is equivalent to the following if statement:

if (o == null)
a == null;
else
o.equals(a);

answered Jul 09 '22 at 09:54

Leaderboard

2

Yes and no. It's more like: "The value of `x` given `if (o == null) x = (a == null); else x = o.equals(a);`" – Federico klez Culloca Jul 09 '22 at 09:59
I don't see ``x`` anywhere in the question though. – Leaderboard Jul 09 '22 at 10:00
1

@Leaderboard that is the point, just `(o==null ? a==null : o.equals(a))` does not mean / do anything, it is either accompanied by an `something = ...` or `return ...`. – luk2302 Jul 09 '22 at 10:01
@Leaderboard I mean that `(o==null ? a==null : o.equals(a))` actually evaluates to something. Your code doesn't. – Federico klez Culloca Jul 09 '22 at 10:01
1

Indeed it doesn't; I was just converting the exact text the OP wrote. Aware in practice that's set to some variable (x in Federico's comment). – Leaderboard Jul 09 '22 at 10:02

1 Answers1