Chapter 15 of the Java Collections Framework introduces the java.util package, which includes essential data structures like lists, sets, and maps, and aims for high performance, interoperability, extensibility, and integration. Key interfaces include Collection, List, Set, Map, SortedSet, and SortedMap, with popular classes being ArrayList, LinkedList, HashSet, TreeSet, HashMap, and TreeMap. An example illustrates the use of ArrayList, demonstrating features like dynamic resizing and support for duplicate elements.

1. Java Collections Framework
Chapter 15: java.util Part 1 - The
Complete Reference

2. Introduction to java.util
• The java.util package contains one of Java's
most powerful subsystems: collections.
• - Collections framework introduced in Java 2.
• - Enhanced by Java 2, version 1.4.
• - Includes data structures like lists, sets, and
maps.

3. Goals of Collections Framework
• - High performance: Efficient implementations
of common data structures.
• - Interoperability: Different collections can
work in similar ways.
• - Extensibility: Easy to adapt and extend
collections.
• - Integration: Arrays can be seamlessly
integrated.

4. Key Interfaces in Collections
• - Collection: Base interface for working with
groups of objects.
• - List: Ordered collection (sequence).
• - Set: Collection of unique elements.
• - Map: Key-value pairs (not a Collection).
• - SortedSet and SortedMap: Sorted collections
and maps.

5. Popular Classes in java.util
• - ArrayList: Dynamic array.
• - LinkedList: Doubly linked list.
• - HashSet: Unordered, unique elements.
• - TreeSet: Sorted set.
• - HashMap: Key-value pairs (unordered).
• - TreeMap: Sorted map.

6. Example: ArrayList
• ArrayList<String> list = new ArrayList<>();
• list.add("A");
• list.add("B");
• System.out.println(list); // Output: [A, B]
• - Dynamic resizing.
• - Allows duplicate elements.