上述所有这些根据操作系统类型和修订版本、一天中的时间、任意用户定义的类、文件中文件、目录或数据的有无等等可以是有条件的。
All of the above can be conditional upon the operating system type and revision, time of day, arbitrary user-defined classes, presence or absence of files, directories, or data in files, and so on.
例如，系统类是不可修改的，而用户定义接口类虽然可以修改，但是不能包含实际的实现代码。
System classes, for instance, are not modifiable, while user-defined interface classes can be modified, but can't include actual implementation code.
类a在系统类装入器的类路径中，而A的超类b，在用户自定义的类装入器的类路径中，这个类装入器是系统类装入器的孩子。
Class a is on the classpath of the system class loader, and a's superclass, B, is on the classpath of a user-defined class loader, which is a child of the system class loader.
以数据记录指针的定位及查询功能的实现为例，详细介绍了使用类设计器将系统控件组合成用户定义控件的方法。
Introduce a way to merge several system controls into a custom control with class designer by the example of implementing record Pointers locating and query function.
以数据记录指针的定位及查询功能的实现为例，详细介绍了使用类设计器将系统控件组合成用户定义控件的方法。
Introduce a way to merge several system controls into a custom control with class designer by the example of implementing record Pointers locating and query function.
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