Programmer Think

1. Introduction Semaphore, a semaphore, holds a series of permissions. Each call to the acquire() method will consume a license, and each call to the release() method will return a license.Semaphore is usually used to limit the number of accesses to shared resources at the same time, which is often referred to as flow restriction.Semaphore sem ...

Today, when studying the Java concurrency container and framework, we can see why we should use ConcurrentHashMap. One reason is: thread unsafe HashMap. HashMap will cause a dead loop when executing put operation concurrently, because multithreading will cause the Entry linked list of HashMap to form a ring data structure and fall into a dead l ...

1, What is Zuul? Zuul is an open source API Gateway server of netflix. It is essentially a web servlet application. The core of Zuul is a series of filters, which can be compared with the Filter of Servlet framework or AOP. Zuul can realize the following functions by loading the dynamic filtering mechanism: Verification and security: Ide ...

Implementation of Spring AOP XML + interface mode enabled XML + custom class implementation Annotation mode on Import dependency: (although this project is not a springboot project, you only need to import the following dependency) <dependency> <groupId>org.springframework.boot</groupId> <artifactId>sprin ...

preface I think the topic of code looping is very interesting. Because as long as developers, they will step through this pit. If you really haven't stepped on it, it only means that you write less code, or you are a real God. Although many times, we try our best to avoid such problems, many times, the dead cycle comes quietly and pits you in ...

Preface: catalogue abstract class 1. What is an abstract class 2. What data type is an abstract class?  3. How are abstract classes defined?  4. Purpose of abstract classes?  5. Can a subclass of an abstract class be an abstract class?  6. Why must an abstract class have a constructor 7. Abstract method 9. Abstract ...

Software testing handout Edit java files using Notepad 1. Configure java path 1.1 select the computer icon / right-click to select the properties of the drop-down menu/ 1.2 select the advanced system Settings link 1.3 select the environment variable button in the system properties window 1.4 select the "classpath" path in the s ...

preface xml messages need to be parsed in project tasks. So I began to learn relevant knowledge. After checking many blog posts, I found a good one, which is very practical. Reprint source: Java Development Notes (109) definition and parsing of XML message The following is the reproduced text, with slight deletion text Although json st ...

Original author: Hollis Character stream, byte stream Bytes and characters Bit is the smallest binary unit and is the operating part of the computer. Value 0 or 1 Byte (byte) is the smallest unit of computer operation data, which is composed of 8 bit s. The value (- 128-127) Char (character) is the smallest readable and writable unit of th ...

Bracket sequence import java.util.*; public class Solution { /** * * @param s string character string * @return bool Boolean type */ public boolean isValid (String s) { // write code here Stack<Character> stack=new Stack<>(); for(char ch:s.toCharArray()) //Convert strin ...