How to transform List to Map with Google collections?

Question

I have a list of strings and I have a function to generate a value for each key in the list.

I want to create a map using this function. Can I do this with Google collec

Answer 1

EDIT: It's entirely possible that Sean's right and I misunderstood the question.

If the original list is meant to be keys, then it sounds like you might be able to just use a computing map, via MapMaker.makeComputingMap, and ignore the input list to start with. EDIT: As noted in comments, this is now deprecated and deleted in Guava 15.0. Have a look at CacheBuilder instead.

On the other hand, that also doesn't give you a map which will return null if you ask it for a value corresponding to a key which wasn't in the list to start with. It also won't give you In other words, this may well not be appropriate, but it's worth consideration, depending on what you're trying to do with it. :)

I'll leave this answer here unless you comment that neither approach here is useful to you, in which case I'll delete it.

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Original answer

Using Guava you can do this pretty easily with Maps.uniqueIndex:

Map map = Maps.uniqueIndex(list, keyProjection);

(I mentioned Guava specifically as opposed to Google collections, as I haven't checked whether the older Google collections repository includes Maps.uniqueIndex.)