The Java Tutorials have been written for JDK 8.Java教程是为JDK 8编写的。Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.本页中描述的示例和实践没有利用后续版本中引入的改进，并且可能使用不再可用的技术。See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.有关Java SE 9及其后续版本中更新的语言特性的摘要，请参阅Java语言更改。
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.有关所有JDK版本的新功能、增强功能以及已删除或不推荐的选项的信息，请参阅JDK发行说明。
This lesson shows how to use a security manager to grant or deny access to system resources for applications. 本课程演示如何使用安全管理器授予或拒绝应用程序对系统资源的访问。The lesson also shows how resource accesses, such as reading or writing a file, are not permitted for applications that are run with a security manager unless explicitly allowed by a permission entry in a policy file.本课程还展示了在使用安全管理器运行的应用程序中，除非策略文件中的权限条目明确允许，否则不允许资源访问（如读取或写入文件）。
The steps for this lesson are:本课程的步骤如下：