Trail: Learning the Java Language
Lesson: Classes and Objects
Questions and Exercises
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Questions and Exercises: Classes

Questions

  1. Consider the following class:

    public class IdentifyMyParts {
        public static int x = 7; 
        public int y = 3; 
    }
    
    1. What are the class variables?

    2. What are the instance variables?

    3. 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

  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. 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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