--Set Java collection interfaces, HashSet implementation class, TreeSet implementation class, LinkedHashSet implementation class

• Set interface belongs to an abstract class
• Set the following two implementation class, HashSet and TreeSet

A, Set Interface

1, Set Overview

• It does not contain a repeat element Collection

2, Set case

• Storage string and ergodic
• Store custom objects and traverse

Two, HashSet implementation class

1, HashSet Class Overview

• We do not guarantee the iteration order of the set
• In particular, it does not guarantee that the order lasts forever

Uniqueness 2, HashSet how packaging elements

• The underlying data structure is a hash table (array element is a linked list)

• Hash table depends on the stored hash value

• Add the underlying functionality relies on two methods:

  int hashCode()

  boolean equals(Object obj)

Three, LinkedHashSet implementation class

1 Overview

• The only element of order
• A list of elements to ensure the orderly
• By a hash table to ensure that the only element

Four, TreeSet implementation class

1 Overview

• Using elemental natural order sort elements
• Or sorted according to a Comparator provided when creating Set
• Configuration depends on the specific method used

2, TreeSet is how to ensure the sort of elements and uniqueness

• The underlying data structure is a red-black tree (red-black tree is a self-balancing binary tree)