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类型 Type

• 创建型 Creational

含义 Intent

The intent of the abstract factory pattern is to provide an interface for creating families of related or dependent objects without specifying their concrete classes

IQueryable 是继承 IEnumerable 的，所以任何使用 IEnumerable 的地方都可以换成 IQueryable. —– 里氏替换

.net - What is the difference between IQueryable and IEnumerable? - Stack Overflow

类型 Type

• 创建型 Creational

含义 Intent

The intent of the factory method pattern is to define an interface for creating an object, but to let subclasses decide which class to instantiate. Factory method lets a class defer instantiation to subclasses.

类型 Type

• 创建型 Creational

含义 Intent

The intent of the singleton pattern is to ensure that a class only has one instance, and to provide a global point of access to it.

短小 Small

函数的第一条规则是要 短小，第二条规则是要 更短小

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例子：

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public static String renderPageWithSetupsAndTearDowns(PageData pageData, boolean isSuite) throws Exception
{
    if (isTestPage(pageData)) {
        includeSetupAndTeardownPages(pageData, isSuite);
    }
    return pageData.getHtml();
}

名副其实 Use Intention-Revealing Names

如下是较好的例子（既有计量对象，也有计量单位）：

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int elapsedTimInDays;
int daysSinceCreation;
int daysSinceModification;
int fileAgeInDays;