bloom filterbloom filter

Maybe Yes, absolute No
A false positive is OK, but a false negative isn’t.

what is diff compareing with HashSet?

• HashSet will give you 100% answer, not maybe

• save space, hashset contain the object itself

• java implementation com.google.common.hash.BloomFilter

application

• at least this many unique items
• testing to see if an element exists on disk before performing any i/o
• type ahead query