Trail: Essential Java Classes基本Java类

This trail discusses classes from the Java platform that are essential to most programmers.本教程讨论了Java平台上的类，这些类对大多数程序员来说都是必不可少的。

➤ Exceptions异常 explains the exception mechanism and how it is used to handle errors and other exceptional conditions.解释异常机制以及如何使用它来处理错误和其他异常情况。This lesson describes what an exception is, how to throw and catch exceptions, what to do with an exception once it has been caught, and how to use the exception class hierarchy.本课程介绍异常是什么，如何抛出和捕获异常，捕获异常后如何处理异常，以及如何使用异常类层次结构。

➤ Basic I/O基本输入/输出 covers the Java platform classes used for basic input and output.介绍用于基本输入和输出的Java平台类。It focuses primarily on I/O Streams, a powerful concept that greatly simplifies I/O operations.它主要关注I/O流，这是一个强大的概念，可以大大简化I/O操作。The lesson also looks at Serialization, which lets a program write whole objects out to streams and read them back again.本课程还将介绍序列化，它允许程序将整个对象写入流，然后重新读取。Then the lesson looks at some file system operations, including random access files.然后，本课程将介绍一些文件系统操作，包括随机访问文件。Finally, it touches briefly on the advanced features of the New I/O API.最后，简要介绍了新I/O API的高级特性。

➤ Concurrency并发性 explains how to write applications that perform multiple tasks simultaneously.说明如何编写同时执行多个任务的应用程序。The Java platform is designed from the ground up to support concurrent programming, with basic concurrency support in the Java programming language and the Java class libraries.Java平台从一开始就被设计为支持并发编程，Java编程语言和Java类库提供了基本的并发支持。Since version 5.0, the Java platform has also included high-level concurrency APIs.自5.0版以来，Java平台还包括高级并发API。This lesson introduces the platform's basic concurrency support and summarizes some of the high-level APIs in the java.util.concurrent packages.本课程介绍平台的基本并发支持，并总结java.util.concurrent包中的一些高级API。

➤ The Platform Environment平台环境 is defined by the underlying operating system, the Java virtual machine, the class libraries, and various configuration data supplied when the application is launched.由底层操作系统、Java虚拟机、类库和启动应用程序时提供的各种配置数据定义。This lesson describes some of the APIs an application uses to examine and configure its platform environment.本课程介绍应用程序用于检查和配置其平台环境的一些API。

➤ Regular Expressions正则表达式 are a way to describe a set of strings based on common characteristics shared by each string in the set.是一种基于集合中每个字符串共享的公共特征来描述一组字符串的方法。They can be used to search, edit, or manipulate text and data.它们可用于搜索、编辑或操作文本和数据。Regular expressions vary in complexity, but once you understand the basics of how they're constructed, you'll be able to decipher (or create) any regular expression.正则表达式的复杂程度各不相同，但一旦您了解了它们的基本构造方法，就可以破译（或创建）任何正则表达式。This lesson teaches the regular expression syntax supported by the java.util.regex API, and presents several working examples to illustrate how the various objects interact.本课程讲授java.util.regex API支持的正则表达式语法，并提供几个工作示例来说明各种对象如何交互。