Adding elements to a set on creation

Question

How can I create a Set in java, and then add objects to it when it is constructed. I want to do something like:

testCollision(getObject(), new HashSet<MazeState>(){add(thing);}); 

But that doesn't seem quite right.

Answer 1

Since Java 7, to instantiate a single-element, immutable Set, you can use:

Collections.singleton(thing); 

Returns an immutable set containing only the specified object. The returned set is serializable.

— Javadoc reference: Collections.singleton(T)

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In Java 8 you can instantiate a Set containing any number of your objects with the following, which is an adaptation of this answer:

Stream.of(thing, thingToo).collect(Collectors.toSet());