The focus of this article
In the previous course, we introduced the three layers of JDK->JRE->JVM in java, where JVM is called the virtual machine of Java, which is only used for execution, and JRE is the operating environment. If you want to run in the operating system, In addition to the JVM, class libraries are required, packages and tools developed by JDK=JRE+. This article will introduce what exactly is the JVM?
JVM
Some people think that the JVM is something in java. This statement is not very correct, because the JVM can only be used if it is not java, and other languages can also use the JVM.
We can understand the JVM as a class specification, that is to say, as long as any language can be compiled into a class specification, then the JVM can execute this language.
JVM can be understood as a virtual computer, which has its own bytecode instructions (assembly language) and memory management (heap, stack, method area, etc.).
Common JVM implementations
If you want to implement JVM, you must meet the corresponding specifications, so there are a lot of JVMs now. We often use the official JVM given by oracle. can explain
In addition to HotSpot, there are other JVMs, as follows:
Jrockit, the fastest JVM in the world