清单 1 中的源代码给出了一个简单的例子，这个环境中中存在火星的地心引力，里面有一个球具有向上的速度。
The source example in Listing 1 shows a simple world with Mars' gravity and a sphere that currently has some upward velocity.
应用程序包含许多无状态会话ejb，一些servlet，两百个JSP，还有大约三百个实用的类，所有这些内容都被包含在一个单一的源代码树里面。
The application contained a dozen stateless session EJBs, several servlets, two hundred JSPs, and about three hundred utility classes, all contained within a single source tree.
这是一个用编制的画图工具，里面有详细的源代码和说明。
This is a preparation using the drawing tools, there are detailed source code and annotations.
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