在超类和子类之间进行等效测试，而无需实例化子类

Question

Just playing with java fundamentals I came up with question whether I can check inheritance between two .class objects without instantiating them.

For example, if I have a class Foo, which is a subclass of Baa: Foo a = new Foo(); return a instanceof Baa Foo a = new Foo(); return a instanceof Baa will return true.

But what do I have to do if I wanna do the equivalent test with Foo.class and Baa.class? I think I can do something like this: Foo.class.newInstance() instanceof Baa.class But would it be possible to test the same without instantiating Foo?

Answer 1

You can use Class.isAssignableFrom(Class) to check the hierarchy in inheritance. According to java-docs:

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter.

This will not instantiate any of the classes and you will get the desired functionality.