Learn about the core JVM architecture in the Java class library

Learn about the core JVM architecture in the Java class library Java Virtual Machine (JVM) is one of the core components in the Java class library.It is the running environment of the Java language, which is used to perform the Java program and provide various functions.This article will introduce the architecture of JVM and its role in the Java class library. The JVM architecture mainly includes the following three parts: class loader, Runtime Data Area, and Execution Engine. 1. Class loader: The class loader is responsible for loading the Java bytecode to the JVM and converted it into a class that can be executed at runtime.The class loader is divided into three levels: bootstrap classloader, extension classloader, and application class loaders (Application Classloader). public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, World!"); } } In the above code, when we run the `HelloWorld` class, the class loader will load this class and create an instance of a` HelloWorld` class, and then execute the code in the `main` method. 2. Data area when runtime: Data area is a area used to store data during the running process of JVM.It includes the method area (Method Area), Heap, Stack, STACK, Program Counter, and Native Method Stack. -Methoth area: Method area for storing structural information, such as running constant pools, fields and method data, constructor, and static variables. -Step: Packing is the largest memory area in JVM for the storage object instance. -Step: The stack is used to store data such as storage methods and local variables.Each thread has an independent stack space. -Ar program counter: The program counter is used to record the byte code instruction address of the current thread. -State method stack: Local method stack is used to execute local methods. 3. Execute engine: The execution engine is responsible for executing bytecode instruction loaded to JVM.It analyzes and executes bytecode instructions one by one.There are two types of executing engines in JVM: interpreter (interpreter) and Just-in-Time Compiler (JIT). -The interpreter: The interpreter explains and executes bytecode instructions one by one.It executes bytecode instructions one by one, but the execution efficiency of the interpreter is low. -JIT compiler: The JIT compiler compiles the hotspot code (frequently executed code) to compile the cost of the machine to improve the execution efficiency. By understanding the JVM architecture, we can better understand the core components in the Java class library.JVM's class loader, runtime data area and execution engine jointly provide strong functions and flexibility for the Java program. It is hoped that this article will help understand the core JVM architecture in the Java library.If you have any questions or need more details, please refer to relevant documents or refer to the official Java document.