说明：  JDK[Java Development Kit，Java开发包，Java开发工具]是一个写Java的applet和应用程序的程序开发环境。它由一个处于操作系统层之上的运行环境还有开发者编译，调试和运行用Java语言写的applet和应用程序所需的工具组成。
(JDK [Java Development Kit, Java Development Kit, Java development tools] is a Java-applet and Writing application program development environment. It consists of a layer above the operating system in the operating environment there are developers to compile, debug and run using Java language to write the applet and applications composed of the necessary tools.)