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by PRO FE S S OR

QUIZ for SECTION V

To find an answer, click on the desired question.

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QUESTION 1:

What is a class ? What is it used for ?

QUESTION 2:

What is an Object ? What are the characteristics of an Object ?

QUESTION 3:

What's the keyword to instantiate a class (create an Object) ?

QUESTION 4:

Can we create more than one Object from a class ?

QUESTION 5:

Convert the following 2 lines of code into only 1 line of code. Quiz test ;
test = new Quiz();

QUESTION 6:

There are 3 lines of code in program below that are used to display a local variable, a class variable(static), and an instance variable (an Object variable). Substitute the XXX, YYY, and ZZZ, for the required expressions to display those variables.
class Quiz
{ static double amount = 21.46;
int number;
public static void main(String[] args)
{ int number = 45;
Quiz test = new Quiz(); // Quiz class is instantiated
System.out.println( XXX ); // displays local variable number 45
System.out.println( YYY ); // displays the class variable amount 21.46
System.out.println( ZZZ ); // displays the instance variable number 0 of the Quiz class } } }

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ANSWER to QUESTION 1:

A class is a template, a blueprint for Objects.

A class is instantiated to create an Object. It accomplishes ENCAPSULATION.

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ANSWER to QUESTION 2:

An Object is an entity, which is an instance of a class.

An Object has:

• Relationship -> It may interact with other Objects
• Identity -> It's unique
• Behavior -> contains methods
• State -> it's initialized

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ANSWER to QUESTION 3:

Keyword: new

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ANSWER to QUESTION 4:

Yes.

A class can be instantiated several times, creating a different object each time.

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ANSWER to QUESTION 5:

Quiz test = new Quiz();

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ANSWER to QUESTION 6:

XXX -> substitute for number
YYY -> substitute for amount or for Quiz.amount
ZZZ -> substitute for test.number

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