Chapter 3: Implementing Classes

Question 1

Where does an object store its data?

Answer 1

an instance variable

Question 2

What is an instance of a class?

Answer 2

an object of the class

Question 3

What are the 3 parts that an instance variable declaration consist of?

Answer 3

1.) an access specifier (private)
2.) The type of the instance variable
3.) The name of the instance variable

Question 4

Write a code for the click method, which advances the counter value by 1

Answer 4

public void click()
{
value = value + 1
}

Question 5

Write the getValue method

Answer 5

public int getValue()
{
return value;
}

Question 6

T/F: Private instance values can only be accessed by methods of the same class.

Answer 6

True

Question 7

What is encapsulation?

Answer 7

the process of hiding implementation details and providing methods for data access

Question 8

What does encapsulation allow a programmer to do?

Answer 8

use a class without having to know its implementation

Question 9

What does information hiding make it easier to do?

Answer 9

locate errors and change implementation

Question 10

What do you need to know before implementing a class

Answer 10

which methods are required

Question 11

What do constructors do?

Answer 11

set the initial data for objects

Question 12

What is the name of a constructor?

Answer 12

the name of the class

Question 13

What are constructors return type?

Answer 13

trick question: constructors have no return type (not even void)

Question 14

What is the name for a constructor that takes no argument

Answer 14

a no-argument constructor

Question 15

What is the following an example of?
public BankAccount()

Answer 15

a no-argument constructor

Question 16

Where do you place constructors and method declarations?

Answer 16

inside a class

Question 17

What are documentation comments used for?

Answer 17

to describe the classes and public methods of your program

Question 18

What is the @param tag used for

Answer 18

methods with no arguments

Question 19

What is the @return tag used for

Answer 19

methods whose return type is void

Question 20

What does the private implementation of a class consist of?

Answer 20

instance variables and the bodies of constructors and methods

Question 21

What is the simple job of a constructor?

Answer 21

to initialize the instance variables of an object

Question 22

What does a unit test do?

Answer 22

verify that a class works in isolation

Question 23

What are the two ways to test a class?

Answer 23

use an environment for interactive testing, or write a tester class to execute test instructions

Question 24

What is a local variable?

Answer 24

a variable that is declared in the body of a method

Question 25

Where are parameter variables declared?

Answer 25

in the method header

Question 26

What happens when a method exits?

Answer 26

its local variables are removed

Question 27

Where do instance variables belong to?

Answer 27

objects (not methods)

Question 28

T/F: You must initialize local variables

Answer 28

True

Question 29

T/F: You must initialize instance variables

Answer 29

False

Question 30

What is the implicit parameter?

Answer 30

the use of the instance variable in a method

Question 31

What reference denotes the implicit parameter?

Answer 31

this

Question 32

T/F: An instance variable shadows a local variable with the same name

Answer 32

False - a local variable shadows an instance variable with the same name.