Articles
Advanced Java

Interview Talk-How to troubleshoot high CPU usage

Computing is indispensable in the program. If the environment is not too bad, the CPU can basically support the application. But if you find that the CPU remains high, you need to think about whether there is a problem with the program.When the server CPU remains high, you can start to locate the problem from the following aspects.Find the pid of the JAVA processMethod 1: jpsThat jar is one of my java programs[root@iZba13i1mo82ot7a3lhq5oZ ~]# jps 17616 Jps 26016 jar 9353 Bootstrap 26028 Bootstra

... Ella
schedule 2 min read
Advanced Java

Explore Java Concurrency-Synchronization Tools

The synchronization tool class is a general concept. It can coordinate the control flow of the thread according to its own state. Understanding the commonly used synchronization tools in JAVA can help developers write better concurrent code.CountDownLatchThe function of a lock is equivalent to a door. Before the door is opened, any thread execution here will be mercilessly detained. Until someone opens the door, the threads blocked outside the door will continue the process behind the door. .imp

... Jackson
schedule 9 min read
Advanced Java

Explore JAVA Concurrency-Concurrent Container Family Portrait

14 concurrent containers, how many have you used?Regardless of multi-threaded concurrency, container classes generally use thread-unsafe classes such as ArrayList and HashMap, which are more efficient. In concurrency scenarios, thread-safe container classes such as ConcurrentHashMap and ArrayBlockingQueue are often used. Although some efficiency is sacrificed, they are safe.The thread-safe containers mentioned above are all under the java.util.concurrent package. There are a lot of concurrent co

... Jameson
schedule 10 min read
Advanced Java

Interview Talk-Talk about your understanding of GC

As a poor JAVA developer, I am often asked in interviews: What kind of rubbish are you? Oh no, do you know the garbage collection mechanism of JAVA?Next, I will make a comprehensive summary of GC. I hope I can confidently answer the interviewer next time: I am the kind that can be recycled by your company.Timing of GCFirst of all, depending on the memory area, the JVM working mode is different, and the GC also has some differences.The new generation (minor GC/young GC)PS: The memory space of the

... Braxton
schedule 4 min read
Advanced Java

Interview Talk-How to troubleshoot memory leaks

JAVA's garbage collection mechanism gives programmers convenience, we don't need to explicitly release resources. But if you want to sit back and relax, you can’t. OOM is like a huanong hidden in the dark, threatening a poor, weak and beautiful programmer.Generally speaking, a healthy program should not have OOM. The objects in memory are in order from birth to death. However, due to some human errors, some objects will often escape the sanctions of the GC, jump out of the GC, and not be in the

... Layla
schedule 4 min read
Advanced Java

Explore Java Concurrency-ThreadLocal

Using ThreadLocal can maintain thread closure, associate a value in the thread with the object that saves the value, and prevent the sharing of variable singleton variables or global variables, but improper use can also cause memory leaks. Learn about it first, and then use it.Speaking from SimpleDateFormatSimpleDateFormat is our commonly used date formatting tool, but friends who are familiar with it all know that it is thread-unsafe.SimpleDateFormat usagepublic class Acuptest { public static v

... Greyson
schedule 8 min read
Core Java

Mybatis connects to mysql database and inserts Chinese garbled characters

There are two situations for the garbled code problem of mysql database:1. mysql database encoding problem (set when building the database).2. The url encoding setting problem for connecting to the mysql database.For the first problem, I currently find that it can only be solved by rebuilding the library. When building the library, choose the UTF-8 character set. I tried to modify the existing database character set to UFT-8, but it doesn't work at all, the inserted Chinese is still garbled (Chi

... Miguel
schedule 2 min read
Core Java

Recommend 5 Java anomaly detection tools

Top Java anomaly detection tools you should knowApplication failures can occur due to various reasons, and there are some tools that can solve every possible error source, such as log management tools, error trackers, performance monitoring solutions, etc. In fact, we have studied this for quite a bit. The different methods found are recorded in production , the most common way to solve the errors in Java applications , how and the tools of application monitoring points can help to detect errors

... Ella
schedule 9 min read
Core Java

IntelliJ IDEA class code template annotation customization

This article provides you with the use of file code templates in the IntelliJ IDEA tutorial. IntelliJ IDEA is an integrated environment for java language development. IntelliJ is recognized as one of the best java development tools in the industry, especially in smart code assistants. , Code automatic prompting, refactoring, J2EE support, Ant, JUnit, CVS integration, code review, innovative GUI design and other functions can be said to be extraordinary. . Interested students can refer to the stu

... Angel
schedule 5 min read
Java Back End Development

How to convert file content into String string

1: use BufferedReadertry { //This method can be used in spring, springBoot environment, or directly new File(path) File keyWordFile = ResourceUtils.getFile("classpath:keyWord.txt"); BufferedReader reader = new BufferedReader(new FileReader(keyWordFile)); //Using StringBuilder is faster, but not safe, because there is only reading here, so it does not affect StringBuilder buffer = new StringBuilder(); String keyWord = null; while ((keyWord = reader.readLine()) != null) { buffer.append(keyWord); }

... Elijah
schedule 3 min read
Java Back End Development

Spring transaction @Transactional in-depth explanation

Hi, everyone, everyone, today I will explain to you the principles of spring framework affairs.There are two methods for spring transaction: configuration file and annotation. The principle of configuration file method will not be introduced too much here. This time I will focus on explaining the principle of annotation @Transactional.One: Annotate the execution principle process of @Transactional:Annotation scanning is performed when the server starts, and all methods with @Transactional are ge

... Layla
schedule 7 min read
Java Back End Development

When gradle + idea is started, an error is reported that the bean cannot be registered, and the service name is duplicated

Error message:The bean'exmafilm.FeignClientSpecification', defined in null, could not be registered. A bean with that name has already been defined in null and overriding is disabled. Action: Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=trueThe meaning of the above error is probably: FeignClientSpecification' defined as null could not be registered. The bean with this name has been defined as null and cannot be overwritten.The

... Paige
schedule 2 min read
Java Back End Development

Java1.8 new time api-LocalDateTime

New time object:1.LocalDate represents the year, month and day 2.LocalTime means hour, minute and second 3.LocalDateTime represents the year, month, day, hour, minute, and second 4. Instant: indicates the time, does not directly correspond to the year, month, and day information, and needs to be converted through time zone 5.ZonedDateTime: Represents the date and time in a specific time zone 6.ZoneId/ZoneOffset: Represents the time zone1. How to get the object //Get the current time through the

... Nathan
schedule 5 min read
Java Back End Development

Three ways for SpringBoolt framework to obtain the value of properties configuration file

Foreword: The Spring framework is a mainstream framework. It is often necessary to configure values ​​in the properties configuration file during use, and sometimes the values ​​need to be obtained in the code. Here are three ways to obtain configuration values:The first way: use the annotation @Value("attribute name") Code: @Value("${jcpt.domain}") private String domain; //Basic platform domain nameError-prone point: If the variable name is modified by static, the value cannot be injected: @Val

... Cameron
schedule 3 min read
Java Back End Development

SpringBoot solves the compatibility problem of internal and external tomcat deployment

Foreword: In the process of using springBoot to develop, we always choose to use the main method in the local class Application to start the service, which is very convenient for local debugging. But the online environment needs to be placed in an external tomcat deployment. At this time, you will find that if you do not do any processing, you cannot start on the external tomcat.So how can the springBoot project be deployed in an external tomcat? This involves the problem of starting the entranc

... Noah
schedule 6 min read
Java Web Development

Memory analysis of arrays in Java

Introduction:At the end of the article, Mo Bai prepared suitable wallpapers for programmers. Those who need them can pick them up. Today's content is to talk to you about the memory analysis and principles of arrays in Java. Many friends may have forgotten it. After all, this is very basic. I've clicked, this time I will review it for everyone!Introduction to memoryThe memory is an important original in the computer, it is a kind of temporary storage area, the function is to run programs. The pr

... Cole
schedule 4 min read
Java Web Development

How to use Code Cloud to build a picture bed of your own?

Introduction: Recently, because I was developing my own small blog, I encountered a problem. When I posted an article on the blog, the pictures were always not uploaded, so I wanted to make a picture bed of my own. There are many, after all, it is domestic, and the access speed is a little faster.Later, I chose Code Cloud. I won't say much. Let's start building your own picture bed with Mo Bai.Prepare the development environment:name of softwareversionGit2.24.0.2-64Code Cloud Warehouse1.0.0Envir

... Mackenzie
schedule 5 min read
Java Web Development

IntelliJ IDEA plug-in, using the one above

Introduction:When you are writing a project, will you feel annoyed by restarting the project every time you modify a line of code? I was very annoyed when I didn't encounter JRebel. Restarting the project would not be too time-consuming if the computer configuration was OK, and vice versa. , I feel bitter, today I recommend an IDEA hot deployment plugin to everyone, see the text below;Hot deployment: It is to upgrade the software while the application is running, but does not need to restart the

... Luis
schedule 6 min read
Java Web Development

If you are still in a hurry for the train ticket home for the Spring Festival, you may wish to read this article

Introduction:As the Spring Festival approaches, many companies have already issued the time for the annual vacation and the exact time for work after the year, but there are still many small partners who have not yet grabbed the tickets for home and return. The annual Spring Festival is when the 12306 burst point. Many people can't get tickets. Not long ago, it was officially reported that 12306 closed the third-party shunt interface. All this year, except for the 12306 official website, it shou

... Lucas
schedule 4 min read
Java Web Development

Using Spring's IOC to realize database CRUD

Introduction:Even if it is the basics, there are still many people who don't; First look at the complete directory structureOpen your graphical interface tool ( sqlyog,navicat...), create a database spring-test, and import the following SQLDROP TABLE IF EXISTS USER; CREATE TABLE USER ( id INT(11) NOT NULL AUTO_INCREMENT, username VARCHAR(32) NOT NULL COMMENT'user name', birthday DATETIME DEFAULT NULL COMMENT'Birthday', sex CHAR(1) DEFAULT NULL COMMENT'Sex', address VARCHAR(256) DEFAULT NULL COMM

... Mark
schedule 5 min read
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