They're not just asking how do you use the HashMap class from the Java Collections API, but they're asking: how does it work internally? The thing is, there's actually a little bit of a trick to this ...

Note that these immutable collections are very different from the immutable collections returned by Java's Collections.unmodifiableCollection() and similar methods. The difference is that Java's ...

Guava is a set of core Java libraries from Google that includes new collection types (such as multimap and multiset), immutable collections, a graph library, and utilities for concurrency, I/O, ...