- `HashMap` : fast, no guarantee of order, allows `null` values and one `null` key - `TreeMap` : Slower than `HashMap`, Guarantees sorted order of keys. - `LinkedHashMap` : Guarantees ordering in which entries were added. - `ConcurrentHashMap` : optimized for multithreaded environment. - `ArrayList` : Random access, fast only for appending at the end, Not suitable for frequent insertions or removals. - `LinkedList` : Slower than `ArrayList`, suitable for frequent insertions or removals. - `Vector` : Synchronized, making it thread-safe, older version of `ArrayList` - `HashSet` : fast, no guarantee of order - `TreeSet` : Slower than `HashSet`, Guarantees sorted order of elements. - `LinkedHashSet` : Guarantees ordering in which entries were added. - `EnumSet` : Optimized for `enum`