Interfaces and Polymorphism - Java Concepts - page 599

6. That variable never refers to a Measurable object. It refers to an object
of some classȌa class that implements the Measurable interface.
7. Both describe a situation where one method name can denote multiple
methods. However, overloading is resolved early by the compiler, by
looking at the types of the parameter variables. Polymorphism is resolved
late, by looking at the type of the implicit parameter object just before
making the call.
8. The String class doesn't implement the Measurable interface.
9. Implement a class StringMeasurer that implements the Measurer
interface.
10. A measurer measures an object, whereas getMeasure measures Ȓitselfȓ,
that is, the implicit parameter.
11. Inner classes are convenient for insignificant classes. Also, their methods
can access variables and fields from the surrounding scope.
12. Four: one for the outer class, one for the inner class, and two for the
DataSet and Measurer classes.
13. The button object is the event source. The listener object is the event
listener.
14. The ClickListener class implements the ActionListener
interface.
15. Direct access is simpler than the alternativeȌpassing the variable as a
parameter to a constructor or method.
16. The local variable must be declared as final .
17. First add label to the panel , then add button .
18. The actionPerformed method does not access that variable.
19. The timer needs to call some method whenever the time interval expires. It
calls the actionPerformed method of the listener object.