Deep understanding of Java Virtual Machines-Java architecture

Java has been used for almost three years, but ashamed to say that Java is the Java language itself, at most, including a JVM, for the entire Java architecture is not very clear, there is now time to In-depth understanding of Java Virtual Machine This book reads, but also answers a lot of doubts.

Java is not only a language, but a series of software and specifications formed by the technical system, we can be based on these technologies to construct Java-compliant virtual machine, language, parser, etc. because Java's original design goal is to achieve "write once, run everywhere" Ideal, the entire software community, inspired by this ideal, has designed different VMs and languages for different scenarios.  for the Java language, today's massively-used Java virtual machines have Oracle company Hotspot,jrocket and IBM's J9 virtual machines. The jrocket is primarily for high-performance scenarios, while J9 is typically embedded in IBM-related products.  broadly speaking, Clojure, JRuby, groovy and other languages and related programs running on Java virtual machines belong to the Java technology system, but in the traditional sense, the Java technology system contains the following parts:  

• Java programming language
• Java virtual machines on a variety of hardware platforms
• class file format
• Java API Class Library
• Third-party Java class libraries from business and open source communities

we refer to the Java programming language, Java Virtual machine, Java API Class library three parts of the JDK (Java Development Kit), JDK is to support Java program development of the smallest environment.  In addition, you can refer to the Java API Class library of Java SE API subset and Java Virtual two parts collectively known as the JRE (Java Runtime enviroment), the JRE is the standard environment to support Java operation.

Deep understanding of Java Virtual Machines-Java architecture