How much do you know about JVM？

JAVA is the most used programming language by developers all over the world. It is a language that occupies the top three positions all the year round, whether it is in the rankings of users' favorite programming languages, programmers' salary list, programming language of choice, etc. , but it is also one of the most difficult languages to learn. In order to help everyone better understand JAVA, the developer community specially launched the "Java Weekly" learning column, which will introduce the latest Java technology and developments, preview activities, hottest questions and answers, live tutorials, etc. The content of this issue is the "JAVA Virtual Machine (JVM)" of several concepts that JAVA developers must know. Let's take a look with the editor!

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How much do you know about the JVM?

【Article recommendation】

Graphical version of JVM logical memory recovery mechanism research >> Click to view

The JVM virtual machine memory recycling machine has confused many people. The text reveals the principle and mechanism of JVM memory recycling from the perspective of JVM implementation mechanism. Thorough analysis from 7 aspects of Java platform logic architecture, JVM physical structure, JVM memory composition structure, Java heap memory structure, etc.!

JVM startup process>>Click to view


The working principle and characteristics of JVM mainly refer to the loading of the operating system into the JVM, which is completed through Java.exe in jdk, and the JVM environment is completed through the following 4 steps. 1. Create JVM loading environment and configuration 2. Load JVM.dll 3. Initialize JVM.dll is linked to the JNIENV (JNI calling interface) instance 4. Call the JNIEnv instance to load and process the class class.



What you must know before learning JVM parameters>>Click to view

The java program runs on the JVM, and the JVM will automatically set some JVM parameters according to the environment, but these parameters cannot be guaranteed to be optimal. Some parameters are basically set at startup, and they cannot be adjusted at runtime. In order for the JVM to run your program better, it is necessary to have a certain understanding of the JVM parameters, and to know in which scenarios these JVM parameters are effective and what role they play. For example, we do not expect classes to be unloaded in the end. You can print some logs during running to help us understand the running status of the JVM, whether it can automatically save some on-site data for us when something goes wrong, etc. These can be set through JVM parameters.

【Troubleshooting】

Regarding the size of the jvm heap, please help.
Under Linux, without configuration, tomcat adjusts jvm to occupy all the memory by default. Why?

Relationship between JMM and JVM

Will the JVM virtual machine adopt the Android ART operating mode in the future?

What is the reason for the inconsistency between the memory occupied by the Tomcat system and the memory occupied by the JVM?

What other languages does the JVM support?