Programmer Think

preface At present, the JDK version used is basically 1.8 or above. In most interviews, you will ask what is the difference between JDK7 and JDK8 versions of HashMap. HashMap is in jdk1 8, the red black tree is added on the basis of array + linked list. What are the benefits of doing so? In this paper, jdk1 8 version of HashMap to do a s ...

JDK1. 8 source code analysis of concurrenthashmap jdk1.8 container initialization Source code analysis There are five construction methods in the ConcurrentHashMap of jdk8. None of the four construction methods initialize the internal array, but deal with the initial values of some variablesThe array initialization of concurrent HashMap of j ...

JDK source code learning 06 currenthashmap analysis The principle of CurrentHashMap is very complex. You can only record what you understand. As we all know, the thread safety implementation principle of CurrentHashMap is Synchronized+CAS. Now let's take a look. Brief reading of notes * Overview: * The main design goal of this hash table is ...

preface I believe that this article is not the first time for my classmates to see articles about HashMap. Most of the online HashMap articles are not suitable for me, so I decided to understand the source code from scratch. I will use the relatively simple logic to convince myself to understand the source code. If you are interested, please l ...

Hashcode & HashMap perturbation function, initialization capacity, load factor, expansion element splitting 1. Why does hashcode use 31 as a multiplier? String. The hashCode method of class is as follows: public int hashCode() { int h = hash; if (h == 0 && value.lengt > 0) { char[] val = value; for (int ...

Why use concurrenthashmap (the disadvantage of HashMap) HashMap is the most commonly used Map class in Java. It has good performance and fast speed, but it can not guarantee thread safety. It can use null value as Key/value The thread insecurity of HashMap is mainly reflected in the dead loop when resizing and fast fail when using iterator In ...

What is a hash table? Hash tables, also known as hash tables, are array based. This indirectly brings an advantage: the time complexity of search is O(1), and of course, its insertion time complexity is also O(1). There is also a disadvantage: the expansion cost is high after the array is created. There is a "mainstream" idea in hash ...

The official account of WeChat: Java essays Follow to learn more about Java related technology sharing. Questions or suggestions, welcome to the official account message! Introduction to HashMap HashMap is mainly used to store key value pairs. It is implemented based on the Map interface of hash table. It is one of the commonly used Jav ...

1. Illustrating data structures 1. Infrastructure (1) Arrays Arrays are essentially a continuous block of memory that holds something in common. Array elements can be quickly positioned and manipulated through array subscripts. However, its insertion and deletion operations are inconvenient, requiring all elements following the insertio ...

hashmap 1.7 capacity expansion occurs before element addition, and 1.8 capacity expansion occurs after element addition Difference between hashmap 1.7 and 1.8 when adding new elements, 1.7 is added to the head and 1.8 is added to the tail. If it exceeds the preset value, it will turn into a red black tree The element subscript calculation of ...