Introduction to the collection framework

Java Collection Framework

Collection Frame :

① the so-called Framework is a collection of class libraries. A set framework is a unified schema used to represent and manipulate a collection, which contains the interfaces and classes that implement the collection;

The different collection classes in the ② collection framework have their own different data structures, so we should choose different collection classes according to the performance requirements of the application.

The ③ collection class is stored in the Java.util package, and the program will use the collection class and the related interface in a large number of programming.

A) iterable: iterator interface;

b) Collection: Class set interface;

c) List: Lists interface;

d) Set: Data set interface;

e) Queue: queues;

f) Map: Key-value pair combination mapping table;

iterable Interface :

① implements this interface to allow an object to be the target of a "foreach" statement, that is, the collection object allows iterations;

② class set interface collection is a sub-interface of iterable, so all class set objects can iterate access, and mapping map does not work;

③ Method:

Iterator<t> Iterator ()

Function: Returns an iterator that iterates over a set of elements of type T;

An iterator is an object of a class that implements the Iterator/listiterator interface, and can access each element of the operation by traversing the set of classes;

Listiterator extends the parent interface iterator, allowing bidirectional traversal of the collection and the ability to modify and delete elements;

Collection Interface :

The class set collection interface defines the method:

①int size ()

②boolean IsEmpty ()

③booean contains (Object o)

④iterator<e> Iterator ()

⑤object[] ToArray ()

⑥boolean Add (e E)

⑦boolean Remove (Object o)

⑧void Clear ()

List, Set, Map

①list interface expands the collection, features: orderly and repeatable ;

②set interface expands the collection, features: unordered and non-repeatable ;

③ Mapping (map) is an object that stores keyword/value pairs. Given a keyword, you can query to get its value, and both the keyword and the value can be objects. The mapping is not a collection sub-interface. So it cannot use iterators to traverse;

Introduction to the collection framework