HashSet, Vector, HashMap and Collection Classes

<< JDK (Java Development Kit) Tutorials

This chapter provides tutorial notes and example codes on collection classes. Topics include collection types: Set, List and Map; data structure types: Array, Linked List, Binary Tree, and Hash Table; commonly used JDK collection classes: HashSet, Vector, HashMap; search operation performance comparison; Comparable interface and compareTo() method.

Types of Collections-of-Elements

Data Structures of Collection Implementations

Collection Implementations in JDK 1.4.1

Search Operation Performance of Different Collection Classes

Comparable Interface and compareTo() Method

Conclusion:

• There are 3 main collection types: Set, List and Map.
• There are 4 main data structures, Array, Linked List, Binary Tree, and Hash Table, for implementing collections.
• JDK 1.4.1 provides 12 collection implementation classes: TreeSet, HashSet, LinkedHashSet, ArrayList, LinkedList, Vector, Stack, TreeMap, HashMap, IdentityHashMap, WeakHashMap, Hashtable.
• HashSet and LinkedHashSet classes have the best performance on search operations.
• TreeSet class requires that objects to be constructed with the Comparable interface.

Sample programs listed in this chapter have been tested with JDK 1.3.1, 1.4.1 and 1.5.0.