CSE 115 Lecture Notes - Lecture 22: List Of North American Broadcast Station Classes, Observer Pattern, Pattern Matching
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Which of the following is not represented in an object diagram: method, object, variable, reference answer: a. method. What is an interface good for? it introduces a type so you can have variable of type. No instantiation: interfaces can not be instantiated; we can not create an instance of. Menukeylistener in the example above because the method has no definition. A class can implement an interface: public class eventhandler implements actionlistener { A class which implements an interface is obligated to provide full definitions of all the methods specified in the interface. Our class now looks like: public class eventhandler implements actionlistener { @override public void actionperformed(actionevent e) { (or in more concrete form): public class eventhandler implements actionlistener { When you define a class, you are defining a type. When you define an interface, you are also defining a type.