如何判断一个类是否等于或扩展另一个类（java）

Question

so I am writing a minecraft mod in which I have successfully added a pistol which works with allot of support classes that handle things like raytracing and sounds and GUI overlays. while the pistol works perfectly, I would like to add support for other mods to add their own weapons using my weapon class as a base class. My problem is how do I get my support classes to know if an item class is actually a custom class that extends my weapon class. Basically what I need to be able to tell is if an instance of a class can be cast to my weapon class for processing using my weapon's base data and functions (note that I am given an instance of the Item class which my WeponItem class extends). Does anyone know of a good way to do this?

Answer 1

if(object instanceof SomeClass)

Answer 2

See 15.20.2. Type Comparison Operator instanceof :

if(someObject instanceof SomeClass)

Learn from JLS , learn from the best.

Answer 3

You can use instanceof to check your type.

Following example may help you

class InstanceofDemo {
public static void main(String[] args) {

    Parent obj1 = new Parent();
    Parent obj2 = new Child();

    System.out.println("obj1 instanceof Parent: "
        + (obj1 instanceof Parent));
    System.out.println("obj1 instanceof Child: "
        + (obj1 instanceof Child));
    System.out.println("obj1 instanceof MyInterface: "
        + (obj1 instanceof MyInterface));
    System.out.println("obj2 instanceof Parent: "
        + (obj2 instanceof Parent));
    System.out.println("obj2 instanceof Child: "
        + (obj2 instanceof Child));
    System.out.println("obj2 instanceof MyInterface: "
        + (obj2 instanceof MyInterface));
}
}

class Parent {}
class Child extends Parent implements MyInterface {}
interface MyInterface {}

Output:

obj1 instanceof Parent: true
obj1 instanceof Child: false
obj1 instanceof MyInterface: false
obj2 instanceof Parent: true
obj2 instanceof Child: true
obj2 instanceof MyInterface: true

Example from reference.

Answer 4

instanceOf should help you do the trick.

if(yourObject instanceof OtherClass)

If you have a object of a unknown class you can also use .getClass() on that object to find out the class. You can also compare two object like this:

if(yourObject instanceof OtherObject)

There are also some other things you should be aware of: http://www.javapractices.com/topic/TopicAction.do?Id=31

Answer 5

You can check if class is instance of your base class:

if (objA instanceof baseObj){

// objA is instance of baseObj

}

Answer 6

You can do like this

Pistol  pistol  = new Pistol ();

if(pistol instanceof Weapon )

Answer 7

Just a note: You really should not do that. You should instead define an interface called Weapon, which all weapons then must implement and which then contains all the methods your program need.