"In-depth understanding of the Java virtual machine: JVM advanced features and best practices" reading notes

The first part goes into Java

1. Enter Java

1 Overview

　　Java is widely used in embedded systems, mobile terminals, enterprise servers, mainframes and other occasions, getting rid of the shackles of hardware platforms and realizing the ideal of "write once, run everywhere"

2, java technology architecture

　　Divide by function

       It includes the following components: Java programming language, Java virtual machines for various hardware platforms, Java API class libraries, third-party Java class libraries from commercial organizations and open source communities, and Class file format

　　The Java programming language, the Java virtual machine, and the Java API class library are collectively referred to as JDK, which is the smallest environment for supporting Java program development.

　　The Java SE API subset and the Java virtual machine in the Java API class library are

　　Divided into 4 platforms according to the fields served by technology

　　Java Card: A platform that supports Java applets running on Java small memory devices (such as smart cards)

　　Java ME: A platform that supports Java programs running on mobile devices

　　Java SE: Support for a platform for desktop applications

　　Java EE: a platform that supports enterprise-level applications using multi-tier architectures