The Java Collections Framework (JCF) is a set of classes and interfaces that implement commonly used data structures like List, Set, Map, and Queue.
It is used to store, manipulate, and retrieve data efficiently. Benefits include:

• Reusability of data structures
• Reduced development time
• Built-in algorithms like sorting and searching

• List → Ordered collection, allows duplicates. Example: ArrayList, LinkedList.
• Set → Unordered collection, does not allow duplicates. Example: HashSet, TreeSet.
• Map → Stores key-value pairs, keys must be unique. Example: HashMap, TreeMap.

• ArrayList → Backed by a dynamic array, fast for accessing elements, slower for insertion/deletion in the middle.
• LinkedList → Backed by a doubly linked list, faster for insertion/deletion, slower for random access.

• HashMap → Stores entries in an unordered manner; allows one null key and multiple null values; faster (O(1) operations).
• TreeMap → Stores entries in sorted order of keys; does not allow null key; slower than HashMap (O(log n) operations).