如何使用课堂 <Interface> Java中的方法签名

Question

I am trying to declare a method, which will take any class implementing an interface as its parameter. Example:

interface ICache {...}
class SimpleCache implements ICache {...}

void doSomething(Class<ICache> cls) { /* Do something with that class */ }

But when I try to call it with SimpleCache.class , it doesn't work. How can I implement this?

Answer 1

如何更改方法签名

void doSomething(Class<? extends ICache> cls) {

Answer 2

You need to introduce a type parameter:

<T extends ICache> void doSomething(Class<T> cls) { /* Do something with that class */ }

In Java, a Class<B> is not a Class<A> even if B inherits from A . That's why it doesn't compile with SimpleCache.class in your case: Class<SimpleCache> is not a Class<ICache> .

Therefore, the solution is to introduce a type T : we're saying that this method can take any class Class<T> where T extends ICache . Since SimpleCache respects that bound, it compiles fine.