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1, Data type 1. Basic data type meaning: The data of the corresponding type is assigned to the variable of the corresponding type Automatic type lifting: Small ----- > Large It can be stored normally, but it may cause a waste of memory Cast type: Large ----- > small Can not occur, which may cause loss of accuracy Small range type variable ...

brief introduction   I believe that the biggest motivation for many people to learn distributed locks is not their own system needs, but the needs of interviewers... Of course, this also shows that the distribution lock is very important. It is often used as an examination question. Before learning, we need to clarify several questions. ...

Mybatis personal summary notes 01 basic information Mybatis is the SQL mapping frameworkThis object can be mapped into a row of data in the databaseDevelopers only need to provide sql, process sql through Mybatis, and finally get the List collection or Java objectsMybatis is a semi-automatic ORM mapping tool, which is called semi-automa ...

Arthas online analysis, diagnosis and tuning tool In the past, when we wanted to troubleshoot online problems, we usually used the tuning tools and commands provided by jdk. The most common is the dump online log, which is then downloaded locally and imported into the jvisual VM tool. There are many changes in this operation. The Arhtas tool d ...

Introduction to JSON JSON(JavaScript Object Notation), namely JavaScript object notation, is a lightweight and general text data format. JSON syntax supports objects, arrays, strings, numbers (int/float), and true/false and null. JSON has a strict format. The main formats are as follows: You can only use double quotation marks, not single quo ...

While the code is rolling, a message pops up in the company's chat tool: "Brother wolf, my machine always FGC frequently..." I quickly opened the dialog box and replied with a witty expression Then continue silently. Then, the little partner smashed a GC log 2019-09-17T20:33:57.889+0800: 4753520.554: [Full GC (Metadata GC Th ...

Introduction This article is based on PY3 8，system win10，numpy1.12. np is the abbreviation of numpy. 1, Summary of reference sources and basic knowledge Performance comparison between python built-in max() and min() functions and Numpy built-in max() and min() functions Based on python 2.7.15 and system win10, the above article draws ...

1 what is LRU cache LRU (Least Recently Used) algorithm is an elimination strategy. In short, the implementation is as follows: put some elements into a container with fixed capacity for access. Due to the limited capacity of the container, the container should ensure that the elements that have been used recently are always in the contain ...

catalogue Spring circular dependency What is circular dependency? Under what circumstances can circular dependencies be handled? Basic introduction and the essence of circular dependency what？ The essence of the problem is actually two sum! How to get to getSingleton method Simple circular dependency (no AOP) Call getSingleton(beanName ...

Operator classification: Arithmetic operator: ① Except (/): class AriTest { public static void main(String[] args) { int num1=12; int num2=5; int result1=num1/num2; double result2=num1/num2; double result3=num1/num2+0.0; double result4=num1/(num2+0.0); double result5=(double)num1/num2; System.out.println(result1); //2 ...