Java includes various mechanisms for iteration, including index (for iterating over an array), cursor (for iterating over the results of a database query), enumeration (in early versions of Java ...

Java’s collections like arrays and lists are foundational building blocks. Functional programming techniques are at times the ideal way to work with these collections.

Apache Collections supports generics, so that's not a reason to choose one over the other. If the collections you need are available in it, I'd probably lean towards Guava, though.