Category: Java

Use interfaces with a single abstract method as lambda targets.

Store dynamic lists with ArrayList for fast random access.

Use LinkedList for frequent insert/remove at ends or as a deque.

Store unique unordered elements with HashSet.

Keep unique elements sorted with TreeSet.

Map keys to values with HashMap for fast lookups.

Store sorted key/value pairs with TreeMap.

Traverse collections safely with Iterator and enhanced for-loops.

Write type-safe classes and methods with generics.

Use Integer, Double, Boolean, and other wrappers for primitives in collections.