Learn about the core JVM development process in the Java class library

The core JVM development process in the Java class library Java virtual machine (JVM) is the core component of the Java platform, which is the operating environment of the Java program.The development process of JVM can be traced back to the birth of the Java language. Through multiple versions and updates, it has continuously evolved and improved to provide better performance and functions. 1. JDK 1.0-1.1： JDK 1.0 was released in 1996. This is the first version of Java language and JVM.JVM is responsible for compiling the Java source code into bytecode and executing bytecode.It contains basic functions such as class loading, bytecode interpreter, and garbage recycling.The design goal of JVM is the irrelevant platform, so that the Java program can run on different operating systems. 2. JDK 1.2-1.3： JDK 1.2 was released in 1998 and introduced the standard version of the Java 2 platform (J2SE).The performance and stability of JVM in this version have improved.In addition, the JIT (JIT) also introduced the JUST-in-Time Compiler (JIT). JIT can compile the hot spot code to the machine code to increase the operating speed.JDK 1.3 further optimized the performance and garbage recovery mechanism of JVM. 3. JDK 1.4-1.6： JDK 1.4 was released in 2002, introducing many new functions and improvements.JVM's garbage recovery mechanism has been upgraded and introduced the Generational Garbage Collection.In addition, the Java Memory Model is introduced to specify the memory access rules of multi -threaded programs. JDK 1.5 (also known as JDK 5.0) was released in 2004.Many important language features are introduced in this version, such as genetics, enums, and automatic boxing (enums) and automatic boxing.There are also some improvements in JVM, including new garbage recychers and JVM monitoring tools. JDK 1.6 was released in 2006, mainly improving the performance tuning, the improvement of the garbage recovery, and the enhancement of memory management. 4. JDK 1.7-1.8： JDK 1.7 was released in 2011 and introduced the support of new garbage recychers (G1 garbage recychers) and dynamic language (such as Scripting API and Nashorn Javascript engines). JDK 1.8 was released in 2014 and is an important version of Java.It introduces functional programming support, including Lambda expression and Stream API.JVM also has some improvements, such as enhanced JIT compilers and support for Metaspace. 5. JDK 9 and later versions: JDK 9 was released in 2017 and is the next main version of the Java platform.The improvement of JVM in this version includes the performance improvement of the JIT compiler, the support of the new garbage recovery (ZGC and Shenandoah) and the PROJECT JIGSAW. Over time, JVM continues to develop in terms of performance, security and function.Java developers can use the rich functions and optimization characteristics provided by JVM to write high -efficiency and reliable Java programs. The following is a simple Java code example, showing how to use JVM garbage recychers: public class GarbageCollectionExample { public static void main(String[] args) { // Create a large object to occupy memory int[] bigObject = new int[1000000]; // The object is no longer cited and becomes garbage bigObject = null; // Forced garbage recycling System.gc(); } } In the above example, we created a large object and placed it to NULL, indicating that the object is no longer cited.We then call the system.gc () method to trigger the garbage recovery.JVM's garbage recovery device will automatically recover the memory occupied by objects that are no longer referenced. Summarize: The development of JVM has gone through multiple versions and continuously improved and improved.Each version brings new features and performance optimization.Java developers can use the rich functions and optimization features provided by JVM to build high -efficiency and reliable Java applications.