Ch8: Interfaces and Polymorphism

Question 1

Define Interface

Answer 1

Formal construction allowing the creation of a set of behaviors a class must fulfill

Question 2

Define Method Signature

Answer 2

Includes name, parameters, and return type of method, but no body

Question 3

What is the default and only allowable access level of interface members

Answer 3

Public

Question 4

___ methods only deal with universal behaviors not dependent on instance properties. Can contain code in its body.

Answer 4

Static

Question 5

A class ____ an interface

Answer 5

Implements

Question 6

Is it possible to create an instance of an interface

Answer 6

No, you may implement an interface, or declare variables and parameters as interface types

Question 7

Name a benefit of using Interfaces

Answer 7

1. You can implement many interfaces at once
2. Can both extend class and implement interface simultaneously
3. Make code usable in wider variety of contexts
4. Decouple code using class from actual class types used

Question 8

Abstract class

Answer 8

Class declared with abstract keyword. Can’t create an object from an abstract class. Can contain method signatures.

Question 9

____ may contain non-constant fields, while ____ can only contain constant fields.

Answer 9

Abstract classes, interfaces

Question 10

Comparable

Answer 10

Allow comparison—in a “greater than” and “less than” sense—to another instance of the class

Question 11

Comparator

Answer 11

Compares two objects of a given class. To allow comparisons and ordering based on the different fields, you can create several different Comparator classes. The class for the compared objects does NOT implement the interface itself.

Question 12

Iterable

Answer 12

Enables iteration over a collection of objects using a for-each loop

Question 13

List

Answer 13

Enables access to objects in a collection by index. In other words, it enables ordered collections.

Question 14

Map

Answer 14

Represents a collection of key/value pairs

Question 15

Define paramaterized interface

Answer 15

Need to specify the class (ex: Comparable; Comparable would compare Job objects)

Question 16

Give an example of an interface extending another interface

Answer 16

List extends Iterable, both of which are implemented by ArrayList class

Question 17

Describe a best practice for testing interfaces

Answer 17

Focus on testing the contract that the interface is supposed to be upholding as opposed to the interface itself