The Java collection class framework has a total of two major interfaces: Collection and Map, one is a collection of elements, and the other is a collection of key-value pairs; among them, the List and Set interfaces inherit the Collection interface, and the other is an ordered collection of elements. , one is a collection of unordered elements; ArrayList and LinkedList implement the List interface, and HashSet implements the Set interface, which are both commonly used.
HashMap and HashTable implement the Map interface, and HashTable is thread-safe, but HashMap performs better; (Recommended learning: java course)
The most basic interfaces in Java collection classes are:
Collection: The root interface of a single-column collection
List: elements are ordered and repeatable
ArrayList: similar to an array with variable length. Suitable for queries, not suitable for additions and deletions
LinkedList: The bottom layer is a two-way circular linked list. Suitable for additions and deletions, not suitable for queries.
Set: The elements are unordered and non-repeatable
HashSet: Determine the position of the element in the set based on the hash value of the object
TreeSet: The elements are stored in the form of a binary tree, which implements the sorting of elements in the collection.
Map: The root interface of a double-column collection, used to store elements with key and value mapping relationships.
HashMap: used to store key-value mapping relationships, no duplicate keys can appear
TreeMap: used to store key-value mapping relationships, no duplicate keys can appear, all The keys are arranged in a binary tree
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