Key Attributes of Common Collection Classes

ArrayList: Fast iteration and fast random access.
Vector: It's like a slower ArrayList, but it has synchronized methods.
LinkedList: Good for adding elements to the ends, i.e., stacks and queues.
HashSet: Fast access, assures no duplicates, provides no ordering.
LinkedHashSet: No duplicates; iterates by insertion order.
TreeSet: No duplicates; iterates in sorted order.
HashMap: Fastest updates (key/value pairs); allows one null key,many null values.
Hashtable: Like a slower HashMap (as with Vector, due to its synchronized methods). No null values or null keys allowed.
LinkedHashMap: Faster iterations; iterates by insertion order or last accessed;allows one null key, many null values.
TreeMap: A sorted map.
PriorityQueue: A to-do list ordered by the elements' priority.