Questions and Exercises: Classes

Questions

  • Consider the following class:
public class IdentifyMyParts {
    public static int x = 7; 
    public int y = 3; 
}
  • What are the class variables?

    • What are the instance variables?

    • 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);
System.out.println("IdentifyMyParts.x = " + IdentifyMyParts.x);

Exercises

  • 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
  • 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.