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Basic introduction of hash table Hash table (also known as hash table) is a data structure that is accessed directly according to the key value. That is, to speed up the search by mapping it to a key in the table. This mapping function is called hash function, and the array storing records is called hash table. (the bottom layer of hash table ...

The jdk used is 1.7. You need to understand the reflection mechanism and the concept of generic bytecode registration! 1, Agent mode Proxy mode is a commonly used java design mode. Its feature is that the proxy class has the same interface with the delegate class. The proxy class is mainly responsible for preprocessing messages for the delega ...

hash 1. Sum of two numbers The idea is to save it in the hash table first, and then judge whether it exists again. Use target - class Solution { public int[] twoSum(int[] nums, int target) { Map<Integer,Integer> map = new HashMap<>(); for(int i = 0;i < nums.length;i++){ if(map. ...

Collection framework A collection of interfaces and classesIn Java Util package Set framework system Collection interface: Stores a non unique, unordered set of objects List interface: Store objects with = = not unique (value repeatable), ordered (insertion order) = = Set interface: Store a set of unique (values cannot be repeat ...

Welcome to my blog to sync updates: Fengshan hospital Source code version 2.4.5-SNAPSHOT Hello, today, let's analyze the core ConcurrentBag of HikariCP, which is the most important core class for managing connection pools. You can see from its name that it is a concurrency management class with very good performance, which is the secret ...

1, Why use JSP The difference between HTML and JSP is like I have a huge wall, and then paste the advertising cloth on it in the traditional way. Today, Zhang San pays 10000 yuan to display his adult products advertisement, and tomorrow, Li Si pays 20000 yuan to display his advertisement for treating kidney deficiency... I have to change the a ...

1. volatile Memory visibility: variables in the main memory will be copied to the thread's private memory when used in a multithreaded environment. Variables modified by volatile keyword can ensure the consistency of the same variables in the main memory and the thread's private memory.No guarantee of atomicity: variables modified by volatile ...

What does springboot automatically configure for us? What can we change? Three core: spring. Factories (various automatic configuration classes)XXAutoConfiguration (autoconfiguration class)Xxproperties (property injection modification) 1. Principle of automatic assembly (most important) pom. Since the import of XML configuration, the core l ...

The second day of Xiaobai's basic java study 1, Notes As the saying goes: if the foundation is not strong, the earth will shake and the mountains will shake. 1. Comment, identifier, keyword notes When the amount of code is small, we can still understand the code we write, but once the project structure is complex, we need comments.Comments ...

In daily development, there are many similar operations of reducing inventory, such as commodity inventory in e-commerce system, prize inventory in lottery system, etc. Solution Using mysql database, use a field to store inventory, and update this field every time you deduct inventory. The database is still used, but the inventory is layere ...