Calling static method on a class?

问题:

Say, I have a reference to a Class object with SomeType having a static method. Is there a way to call that method w/o instantiating SomeType first? Preferably not escaping strong typing.

EDIT: OK, I've screwed up.

interface Int{
    void someMethod();
}

class ImplOne implements Int{
    public void someMethod() {
        // do something
    }
}

Class<? extends Int> getInt(){
    return ImplOne.class;
}

In this case someMethod() can't be static anyways.

回答1:

A static method, by definition, is called on a class and not on an instance of that class.

So if you use:

SomeClass.someStaticMethod()

you are instantiating nothing (leave aside the class loading and instantiation of the SomeClass class itself, which the JVM handles and is way out of your scope).

This is opposed to a regular method called on an object, which has already been instantiated:

SomeObject o = someObject; // had to be instantiated *somewhere*
o.someMethod();

回答2:

I'm not sure exactly what the situation is, but if you're looking to execute the static method on a class without knowing the class type (i.e. you don't know it's SomeType, you just have the Class object), if you know the name and parameters of the method you could use reflection and do this:

Class c = getThisClassObjectFromSomewhere();

//myStaticMethod takes a Double and String as an argument
Method m = c.getMethod("myStaticMethod", Double.class, String.class);
Object result = m.invoke(null, 1.5, "foo");

回答3:

Since you talk about a Class object, I assume that you're interested in Java reflection. Here's a brief snippet that does what you're trying to do:

Class someClass = SomeType.class;
Method staticMethod = someClass.getMethod( "methodName", ... );

// pass the first arg as null to invoke a static method
staticMethod.invoke( null, ... );

回答4:

Yes. That's what static methods are all about. Just call it. SomeType.yourStaticMethodHere().