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Trail: Learning the Java Language
Lesson: Classes and Objects
Classes and Objects
Classes
Declaring Classes
Declaring Member Variables
Defining Methods
Providing Constructors for Your Classes
Passing Information to a Method or a Constructor
Objects
Creating Objects
Using Objects
More on Classes
Returning a Value from a Method
Using the this Keyword
Controlling Access to Members of a Class
Understanding Instance and Class Members
Initializing Fields
Summary of Creating and Using Classes and Objects
Questions and Exercises
Questions and Exercises
Nested Classes
Inner Class Example
Summary of Nested Classes
Questions and Exercises
Enum Types
Questions and Exercises
Annotations
Questions and Exercises
Home Page > Learning the Java Language > Classes and Objects
Questions and Exercises: Classes

### Questions

> 1. Consider the following class:

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

> > a. What are the class variables?

> > b. What are the instance variables?

> > c. What is the output from the following code:

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

### Exercises

> 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 Enum Types.

> > Hint : You can use the `assert` statement to check your assignments. You write:

> > >     assert (boolean expression to test);

> > If the boolean expression is false, you will get an error message. For example,

> > >     assert toString(ACE) == "Ace";

> > should return `true`, so there will be no error message.

> > If you use the `assert` statement, you must run your program with the `ea` flag:

> > >     java -ea YourProgram.class

> 2. Write a class whose instances represent a full deck of cards. You should also keep this solution.

> 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.

Check your answers.

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