Questions and Answers
A polymorphic reference is one that can refer to _______________ type(s) of object(s).
multiple
In Java, polymorphic method binding occurs ____________________.
at run-time
In Java, a(n) ___________________ is a collection of constants and abstract methods.
interface
Which of the following is true regarding the method call spot.speak() with Animal spot = new Dog();?
Signup and view all the answers
What will the following method call a.compareTo(b) return if Object a is larger than Object b?
Signup and view all the answers
In order to create a class that implements an interface, the __________________ keyword is used.
Signup and view all the answers
What will happen if you try to call a.wagTail() when a is declared as Animal a = new Dog();?
Signup and view all the answers
The commitment to execute certain code to carry out a method invocation is referred to as ______________.
Signup and view all the answers
It is possible to create an object by instantiating the Animal interface.
Signup and view all the answers
A parameter to a method can be polymorphic.
Signup and view all the answers
An interface cannot declare any instance variables.
Signup and view all the answers
If a class implements an interface, it cannot extend another class.
Signup and view all the answers
How does inheritance support polymorphism?
Signup and view all the answers
What is the difference between a class and an interface?
Signup and view all the answers
Describe the Comparable interface.
Signup and view all the answers
Study Notes
Polymorphism
- Polymorphic reference can refer to multiple types of objects.
- In Java, polymorphic method binding occurs at run-time, meaning the method invoked is determined by the object’s actual type.
Interfaces
- An interface in Java consists of constants and abstract methods.
- A class implementing an interface uses the "implements" keyword.
Method Overriding
- If a Dog class overrides a method from a parent Animal class, calling
spot.speak()will invoke the Dog's overridden method. - If the Dog class implements the Animal interface with an additional method
wagTail, trying to calla.wagTail()will result in a compile-time error becausewagTail()is not defined in the Animal interface.
Object Comparison
- The
compareTomethod will return a number greater than 0 if the first object is larger than the second, zero if they are equal, or less than 0 if the first is smaller.
Binding and Instantiation
- Binding refers to the commitment to execute certain code for a method invocation.
- It is false that an object can be instantiated from an interface; interfaces cannot be instantiated.
- It is true that methods' parameters can be polymorphic, allowing for various object types.
Class vs. Interface
- A class can be instantiated, while an interface cannot.
- A class that implements an interface can still extend another class.
Comparable Interface
- The Comparable interface includes a method called
compareTothat returns three possible values: greater than 0, equal to 0, or less than 0, indicating the comparative result between objects.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your understanding of Java polymorphism and interfaces with this quiz. It covers key concepts such as polymorphic references, method binding at run-time, and the structure of interfaces in Java. Perfect for any Java programming student!
