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Quick Intro to Java Collections
This document provides a quick introduction to Java collections, including the core Collection interface and three main collection types: List, Set, and Map. It describes some key methods of the Collection interface like add(), remove(), and contains(). It also outlines some common concrete classes that implement the List, Set, and Map interfaces, such as ArrayList, LinkedList, HashSet, TreeSet, HashMap, and TreeMap. The document concludes by demonstrating how to iterate over a collection using an Iterator.
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Quick Intro to Java Collections
- 1. Quick Intro to Java Collec2ons Jussi Pohjolainen Tampere University of Applied Sciences
- 2. Intro • Java Collec2on Framework is a set of classes and interfaces to implement data structures • When array is not enough.. J • Lot of classes and interfaces – hFp://upload.wikimedia.org/wikipedia/ commons/4/41/Collec2on_Classes.jpg
- 3.
- 4. Collec2on Interface • Basic parts of all collec2ons • add(), remove(), toArray(), contains() • Collec2on is generic
- 5. Three main type of Collec2on • List – Always ordered, may contain duplicates, like an array • Set – Cannot contain duplicate • Map – Key – value pairs, random access to keys
- 6. List • List interface has two concrete classes – ArrayList – implementa2on uses dynamically resized arrays – LinkedList – double-‐linked list
- 7. Set • Set can’t have duplicates • Couple concrete classes – HashSet – TreeSet – sorted elements!
- 8. Map • Key value pairs • Couple concrete classes – HashMap – TreeMap -‐ sorted
- 9. How to iterate? • Use an iterator! Iterator i = someCollection.iterator(); while(i.hasNext()) { System.out.println(i.next()); }