Inheritance: Annotations — Single table, joined table, and table per class.

继承：标注——单个表、联合表和按类表。

youdao

Classes can be derived from only a single class, but they can implement multiple interfaces.

类只可以从一个单一的类派生，但它们可以实现多个接口。

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Grails gives you a place to store commonly used methods that transcend any single domain class: services.

Grails为您提供了保存常用方法的位置，并且超越了任何单个的域类：即服务。

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He says the class action failed because it did not target a single action or policy by Wal-Mart.

VOA: special.2011.06.24

Netscape and Opsware, which he helped found, went public with single-class share structures in 1995 and 2001, respectively.

WSJ: In Silicon Valley, Founders Fight for Control

But with B-share holders calling the shots, such firms tend to underinvest, leading to lower sales growth and valuations than with single-share-class firms, according to a study by Harvard Business School's Paul Gompers, Stanford's Joy Ishii and Wharton's Andrew Metrick.

FORBES: Magazine Article

Three of the four worst returns occurred in single-asset class portfolios.

FORBES: The Multiple Rewards of Multi-Asset-Class Investing