How does HashMap work?
The principle is introduced as follows:
HashMap is implemented based on the Hash algorithm.
(Online learning video tutorial sharing: java video tutorial)
When using the put(key,value) method, HashMap will be obtained based on the key.hashCode() method Get the hash value of the key, and then find the corresponding bucket position based on the hash value. If there is already an element in this area, another euqal() comparison will be done. If they are equal, the new addition will fail because HashMap does not allow the same key value. , if not equal, it is just a simple hash conflict.
Before JDK1.8, HashMap will store this element in the next node of the linked list. HashMap stores key-value pairs in each linked list node. After JDK1.8, HashMap added a red-black tree, so when the number of linked list nodes exceeds 8, it will be converted from the linked list to a red-black tree, and once it is less than 8, it will be converted from the red-black tree back to the linked list.
Recommended related article tutorials: java quick start
The above is the detailed content of How does HashMap work?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1387
52
What is the expansion mechanism of hashmap?
Mar 15, 2023 pm 03:39 PM
The expansion mechanism of hashmap is to recalculate the capacity and replace the original array with a new array. Recalculate all the data of the original array and insert a new array, and then point to the new array; if the array has reached the maximum value before capacity expansion, directly set the threshold to the maximum integer and return it.
How to insert key-value pairs into HashMap using put() method of HashMap class
Jul 26, 2023 pm 11:53 PM
How to insert key-value pairs into a HashMap using the put() method of the HashMap class. HashMap is a very important class in the Java collection framework. It provides a way to store key-value pairs. In actual development, we often need to insert key-value pairs into HashMap, which can be easily achieved by using the put() method of the HashMap class. The signature of HashMap's put() method is as follows: Vput(Kkey,Vvalue)
Based on Java HashMap, how to solve the problem of inserting duplicate Key values
May 09, 2023 am 10:52 AM
Inserting duplicate Key values in javaHashMap To insert duplicate values in HashMap, you first need to figure out how elements are stored in HashMap. Each element stored in the put method Map is a key-value pair, and they are all added through the put method, and the same key will only have one associated value in the Map. The put method is defined as follows in Map. Vput(Kkey,Vvalue); put() method implementation: first hash(key) gets the hashcode() of the key, and hashmap finds the chain where the position to be inserted is based on the obtained hashcode.
Interpretation of Java documentation: Detailed explanation of usage of containsKey() method of HashMap class
Nov 04, 2023 am 08:12 AM
Interpretation of Java documentation: Detailed explanation of the usage of the containsKey() method of the HashMap class. Specific code examples are required. Introduction: HashMap is a commonly used data structure in Java. It provides efficient storage and search functions. The containsKey() method is used to determine whether the HashMap contains the specified key. This article will explain in detail how to use the containsKey() method of the HashMap class and provide specific code examples. 1. cont
What is the difference between LinkedHashMap and HashMap in java
May 02, 2023 am 08:31 AM
1. Explain that Map can basically use HashMap, but HashMap has a problem, that is, the order of iterating HashMap is not the order in which HashMap is placed, or it is out of order. This shortcoming of HashMap often causes trouble, because in some scenarios we expect an ordered Map, which is LinkedHashMap. 2. Difference instances publicstaticvoidmain(String[]args){Mapmap=newLinkedHashMap();map.put("apple","Apple");map.put("
Java adds a Map to another Map using the putAll() function of the HashMap class
Jul 24, 2023 am 09:36 AM
Java uses the putAll() function of the HashMap class to add a Map to another Map. Map is a commonly used data structure in Java and is used to represent a collection of key-value pairs. In Java's collection framework, HashMap is a commonly used implementation class. It provides the putAll() function, which is used to add one Map to another Map to facilitate data merging and copying. This article will introduce how to use the putAll() function and provide corresponding code examples. first,
Java Map performance optimization revealed: Make your data operations faster and more efficient
Feb 20, 2024 am 08:31 AM
JavaMap is a commonly used data structure in the Java standard library, which stores data in the form of key-value pairs. The performance of Map is crucial to the running efficiency of the application. If the performance of Map is poor, it may cause the application to run slowly or even crash. 1. Choose the appropriate Map implementation Java provides a variety of Map implementations, including HashMap, TreeMap and LinkedHashMap. Each Map implementation has its own advantages and disadvantages. When choosing a Map implementation, you need to choose the appropriate implementation based on the specific needs of the application. HashMap: HashMap is the most commonly used Map implementation. It uses hash tables to store data and has faster insertion, deletion and search speeds.
How to use HashMap to cache data in Java singleton mode
May 13, 2023 am 09:43 AM
1. What is the singleton pattern? The singleton pattern is an object creation pattern that is used to generate a specific instance of an object. It can ensure that only one instance of a class in the system is generated. The singleton implemented in Java is within the scope of a virtual machine. Because the function of loading a class belongs to the virtual machine, a virtual machine will create an instance of the class when it loads the singleton class through its own ClassLoad. In the Java language, such behavior can bring two major benefits: 1. For frequently used objects, the time spent on creating objects can be omitted, which is a very considerable system overhead for those heavyweight objects; 2. Since the number of new operations is reduced, the frequency of system memory usage will also be reduced, which will reduce GC pressure.
