Java是否具有“是一种类”？测试方法 [英] Does Java have an "is kind of class" test method

问题描述

我有一个基类， Statement ，其他几个类继承，名为 IfStatement ， WhereStatement 等等...在 if 语句中执行测试的最佳方法是什么，以确定哪种 Statement 类实例派生自？

I have a baseclass, Statement, which several other classes inherit from, named IfStatement, WhereStatement, etc... What is the best way to perform a test in an if statement to determine which sort of Statement class an instance is derived from?

推荐答案

if (obj.getClass().isInstance(Statement.class)) {
   doStuffWithStatements((Statement) obj));
}

关于这种技术的好处（而不是instanceof关键字）是你可以将测试类作为对象传递。但是，是的，除此之外，它与instanceof相同。

The nice thing about this technique (as opposed to the "instanceof" keyword) is that you can pass the test-class around as an object. But, yeah, other than that, it's identical to "instanceof".

注意：我故意避免编辑类型实例检查是否是正确的要做的事情。是的，在大多数情况下，最好使用多态。但这不是OP所要求的，我只是在回答他的问题。

NOTE: I've deliberately avoided editorializing about whether or not type-instance-checking is the right thing to do. Yeah, in most cases, it's better to use polymorphism. But that's not what the OP asked, and I'm just answering his question.

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