Structuring Data with Java - Java - page 235

The Collections Framework

Problem

You're having trouble keeping track of all these lists, sets, and iterators.

Solution

There's a pattern to it. See Figure 7-1 and Table 7-1 .

Discussion

List , Set , and Map are the three fundamental data structures of the Collections Framework.
List and Set are both sequences, with the difference that List preserves order and allows
duplicate entries, whereas Set , true to the mathematical concept behind it, does not. Map is a
key/value store, also known as a “hash,” a “dictionary,” or an “associative store.”

Figure 7-1 , in the fashion of the package-level class diagrams in the O'Reilly classic Java in
a Nutshell , shows the collection-based classes from package java.util .

See Also

The javadoc documentation on Collections , Arrays , List , Set , and the classes that imple-
ment them provides more details than there's room for here. Table 7-1 may further help you
to absorb the regularity of the Collections Framework.

Table 7-1. Java collections

Interfaces Resizable array Hashed table Linked list Balanced tree

Set HashSet TreeSet

List ArrayList, Vector LinkList

Map HashMap, HashTable TreeMap