Answers to Questions and Exercises: Creating Classes - Java Tutorial 5.0 英文版

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Answers to Questions and Exercises: Creating Classes

Questions

Question 1: Consider the following class:

public class IdentifyMyParts {
    public static int x = 7;
    public int y = 3;
} 

Question 1a. How many class variables does the IdentifyMyParts class contain? What are their names?
Answer 1a: 1, x

Question 1b. How many instance variables does the IdentifyMyParts class contain? What are their names?
Answer 1b: 1, y

Question 1c. What is the output from the following code:

IdentifyMyParts a = new IdentifyMyParts(); 
IdentifyMyParts b = new IdentifyMyParts(); 
a.y = 5; 
b.y = 6; 
a.x = 1; 
b.x = 2; 
System.out.println("a.y = " + a.y); 
System.out.println("b.y = " + b.y); 
System.out.println("a.x = " + a.x); 
System.out.println("b.x = " + b.x); 

Answer 1c: Here is the output:

 a.y = 5 
 b.y = 6 
 a.x = 2 
 b.x = 2 

Exercises

Exercise 1: Write a class whose instances represent a single playing card from a deck of cards. Playing cards have two distinguishing properties: rank and suit. Be sure to keep your solution as you will be asked to rewrite it in Enumerated Types.
Answer 1: Card.java

Exercise 2: Write a class whose instances represents a full deck of cards. You should also keep this solution.
Answer 2: See Deck.java .

Exercise 3: Write a small program to test your deck and card classes. The program can be as simple as creating a deck of cards and displaying its cards.
Answer 3: See DisplayDeck.java .

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