Shulou(Shulou.com)06/01 Report--

This article will explain in detail how to carry out HashMap source code analysis, the content of the article is of high quality, so the editor will share it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

The code is based on JDK 1.8

Cardinal knowledge

Map is a data collection interface that holds Key-Value key-value pairs. HashMap is a Map implementation based on HashCode. Because HashCode is based on Key for storage, Key is unique in HashMap.

All Key,Value in HashMap can be null.

Source code parsing class declaration 1

two

three

Public class HashMap extends AbstractMap implements Map, Cloneable, Serializable {

/ /...

}

Map-AbstractMap itself implements the Map interface, and here it is emphasized again that HashMap implements Map

Cloneable implements the clone interface.

Serializable implements the serialization interface

Data structure 1

two

three

four

five

six

seven

eight

nine

ten

eleven

twelve

thirteen

fourteen

fifteen

sixteen

seventeen

eighteen

nineteen

twenty

/ * *

* table is initialized when it is used for the first time and resized if necessary.

* when allocating size, the length is always a power of 2

, /

Transient Node [] table

/ / Node static inner class, linked list data structure

Static class Node implements Map.Entry {

Final int hash

Final K key

V value

Node next

Node (int hash, K key, V value, Node next) {

This.hash = hash

This.key = key

This.value = value

This.next = next

}

}

The above code describes the underlying data structure of HashMap: array + linked list.

In 1.8, red and black trees were added, with detailed study.

Constructor function

For constructors, several overloads are provided to facilitate the creation of instances:

one

two

three

four

Public HashMap ()

Public HashMap (int initialCapacity)

Public HashMap (int initialCapacity, float loadFactor)

Public HashMap (Map

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.