Question

• Comment your code. At the top of the program include your name, a brief description of the program and what it does and the due date.
• The program must be written in Java and submitted via D2L.
• The code matches the class diagram given above.
• The code uses Inheritance.

In the following, you are given code for two classes: Coin and TestCoin. You study these classes first and try to understand the meaning of every line. You can cut and paste the code to Eclipse and run it.

The following Java codes are adapted from (John Lewis and William Loftus (2007). “Software Solutions Foundations of Program Design, 5^th edition”, Pearson Education, Inc. pp. 220-222).

public class Coin {

                  private final int HEADS = 0;

                  private final int TAILS = 1;

                  private int face;

                 

                  public Coin(){

                                    flip();

                  }

                 

                  public void flip(){

                                    face = (int)(Math.random()*2);

                  }

                 

                  public boolean isHeads(){

                                    return (face == HEADS);

                  }

                 

                  public String toString(){

                                    String faceName;

                                    if(face == HEADS){

                                                      faceName = "Heads";

                                    }else{

                                                      faceName = "Tails";

                                    }

                                    return faceName;

                  }

}

public class TestCoin {

                 

                  public static void main(String[] args) {

                                    Coin myCoin = new Coin();

                                    myCoin.flip();

                                    System.out.println(myCoin);

                                    if(myCoin.isHeads()){

                                                      System.out.println("The coin has head and you win.");

                                    }else{

                                                      System.out.println("The coin has tail and you lose.");

                                    }

                  }

}

To help your understanding, I give the following brief explanation. The Coin class stores two integer constants (HEADS and TAILS) that represent the two possible states of the coin, and an instance variable called face that represents the current state of the coin. The Coin constructor initially flips the coin by calling the flip method, which determines the new state of the coin by randomly choosing a number (either 0 or 1). Since the random() method returns a random value in the range [0-1) (the left end is closed and the right end is open), the result of the expression (int)(Math.random()*2) is a random 0 or 1. The isHeads() method returns a Boolean value based on the current face value of the coin. The toString() method uses an if-else statement to determine which character string to return to describe the coin. The toString() method is automatically called when the myCoin object is passed to println() in the main method.

The TestCoin class instantiates a Coin object, flips the coin by calling the flip method in the Coin object, then uses an if-else statement to determine which of two sentences gets printed based on the result.

After running the above two classes, the following is one of the possible outputs:

Tails

The coin has tail and you lose.

Design and implement a new class MonetaryCoin that is a child of the Coin class

The new class should satisfy the following requirement. Besides all the features existed in the Coin class, the MonetaryCoin will have an extra instance variable called value to store the value of a coin. The variable value is the type of integer and has the range of 0-10. The derived class should also have an extra method getValue() that returns the value. The new class should have two constructors: one is the no-argument constructor MonetaryCoin(), the other takes one parameter aValue of integer that is used to initialize the instance variable value. According to good practice, in the body of constructor, the first line should call its super class’ no-arg constructor. To demonstrate that your new class not only has the old feature of keeping track of heads or tails but also has the new feature of keeping track of value, you should overwrite/override the method toString(). The specification for the new toString() is:

              Header: String toString()

              This method gives values of all instance variables as a string.

              Parameters: no.

              Precondition: no.

              Returns: a string that takes one of the following value:

              If the face is 0, value is x (here it represents an integer in the range 0..10).

                   The returned string should be “The coin has head and value is x.”

              If the face is 1, value is x,

                   The returned string should be “The coin has tail and value is x.”

As a summary, this class should have four methods:

              Constructor: public MonetaryCoin()

      Constructor: public MonetaryCoin(int aValue)    

      Getter method: public int getValue()

      toString method: public String toString()()

Answer 1

package HomeworkLib1;

public class MonetaryCoin extends Coin{
        private int value;
        MonetaryCoin(){
                super();
                this.value = 0;
        }
        MonetaryCoin(int aValue){
                super();
                if(aValue>=0 && aValue<=10)
                        this.value= aValue;
        }
        public int getValue() {
                return this.value;
        }
        public String toString() {
                String str="";
                if(this.isHeads()) {
                        str += str + "The coin has head and the value is " + this.getValue();
                }
                else
                        str += str + "The coin has tail and the value is " + this.getValue();
                return str;
        }
}

package HomeworkLib1;

public class TestCoin {
    public static void main(String[] args) {
                      Coin myCoin = new Coin();
                      myCoin.flip();
                      System.out.println(myCoin);
                      if(myCoin.isHeads()){
                                        System.out.println("The coin has head and you win.");
                      }else{
                                        System.out.println("The coin has tail and you lose.");
                      }
                      MonetaryCoin mc = new MonetaryCoin();
                      mc.flip();
                      System.out.println(mc);
                      mc = new MonetaryCoin(5);
                      mc.flip();
                      System.out.println(mc);
                      mc.flip();
                      mc.flip();
                      System.out.println(mc);
    }

}