本文假设您熟悉EJB 3.0基本概念和对象关系(OR)映射基本概念。(若需了解这两个主题的更多信息，请参阅参考资料)。

This article assumes that you're familiar with basic EJB 3.0 and object-relational (or) mapping concepts (see Resources for more information on both subjects).

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类提供软件概念和实体的结构，而对象是类的真实的实例。

Classes provide the structure for software concepts or entities, whereas objects are live instances of classes.

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我们在前面看到Scala有声明对象的概念，我们会在“类和对象：状态哪里去了？”章节来讨论它们。

We saw previously that Scala has the concept of a declared object, which we'll dig into in the section called "Classes and Objects: Where are the Statics?".

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PROFESSOR: Last time, Professor Guttag introduced the idea of objects and classes and this wonderful phrase called object-oriented programming.

教授：上节课，Guttag教授,介绍了对象和类的概念以及,面向对象编程这个美妙的短语,这是我今天想继续讲的一个话题。

麻省理工公开课 - 计算机科学及编程导论课程节选