AP Computer Science Homework Set 7 Inheritance

Transcription

1 AP Computer Science Homework Set 7 Inheritance P7A. You ve been hired to design the next generation electronic device. Write the class definition for a new type of object of your own created design that extends MyDevice. The class definition should: a. include a unique instance variable or variables and/or processor methods (to justify it as a new subclass), b. include an upgraded multi-argument constructor to reflect the addition of the new instance variable(s), c. add new getters and setters for each new instance variable(s), and d. include a tostring() method that overrides the superclass tostring() method to include the values of all private instance variables in its output. Include your new device in the ArrayList<MyDevice>. Traverse the ArrayList<MyDevice> using either a for or for-each loop and call each object s tostring() method. The ArrayList below includes seemingly different objects. However, since they all extend MyDevice, they are all really considered MyDevice objects and can therefore be placed into the ArrayList<MyDevice>; that is, they can all fit into the ArrayList of MyDevices. The for loop below polymorphically processes (prints out) the all of the devices in the ArrayList<MyDevice>. This means that the loop can treat all objects that are seemingly different (poly-morphism many shapes ) as MyDevice objects and call their respective tostring() methods. for( MyDevice device : inventory ) System.out.println( device ); } // end for polymorphism in action! We never refer to specific phones, pods, pads, etc. We only refer to them as a device /poly mor phism/ - n. 1. the act of referring to a subclass object using a superclass name, 2. the act of referring to objects in the general as opposed to the specific. Page 1

2 P7B. Consider the Television class on the next page. Write a program that will include the following: a. Write four new classes, Plasma, DLP, LCD, and LED that extend the Television class shown below. b. For each of the above classes: i. Write a zero argument constructor for each of the above classes. ii. Write a new two argument constructor for each of these four classes that take a String argument for the model of the Television and a double for the cost of the television. c. Write a driver program to create each one of these types of Televisions, including a Television object and store them into an ArrayList of type Television. Use a for-each loop to polymorphically call the tostring() method for each Television in the ArrayList. Sample output is shown below: Page 2

3 public class Television private String model; private double price; public Television() this.model = new String(); this.price = 0.0; } // end zero-arg constructor Television public Television( String initialmodel, double initialprice ) this.model = new String( initialmodel ); this.price = initialprice; } // end two-arg constructor Television public void setmodel( String newmodel ) this.model = newmodel; } // end method setmodel public String getmodel() return this.model; } // end method getmodel public void setprice( double newprice ) this.price = newprice; } // end method setprice public double getprice() return this.price; } // end method getprice public String tostring() String output = new String(); output = "The Model of this tv is: " + this.model +"\tprice: " + this.price; return output; } // end method tostring } // end class Television Page 3

4 P7C. Below is a class definition for the abstract class SuperHero. public abstract class SuperHero private String suitcolor; private boolean hascape; public SuperHero() this.suitcolor = new String(); this.hascape = false; } // end zero-arg constructor SuperHero public void setsuitcolor(string suitcolor) this.suitcolor = new String( suitcolor ); } // end method setsuitcolor public String getsuitcolor() return suitcolor; } // end method getsuitcolor public void setcape(boolean cape) this.hascape = cape; } // end method setcape public boolean iscaped() return hascape; } // end method iscaped public abstract String motto(); } // end abstract class SuperHero Page 4

5 Part 1: Write class definitions for an AsteroidMan, FriedEggMan, and another superhero of your choosing that extends the abstract class SuperHero. Each of these classes should implement the motto() method that returns a simple motto unique to their class (create your own custom and clever mottos!) Part 2: Write a SuperHeroDriver class that creates instances of an AsteroidMan, FriedEggMan, and YourHero and initializes each of them with an arbitrary suitcolor and hascape instance variable. Add each of these Superheroes to an ArrayList of type SuperHero called heroes and print each superhero s suitcolor, hascape instance variable, and motto using a for-each loop. Part 3: Create 3x3 2D array called capedheroes that can hold objects of type SuperHero. For every superhero in the heroes ArrayList that has a cape, add that SuperHero to the capedheroes 2D array starting at (0,0) AND remove that SuperHero from the Superheroes ArrayList. Empty spaces in the 2D array should be filled with the value of null. Use a separate nested for loop to perform this operation. Your algorithm should work for any number of heroes in the original ArrayList of SuperHero. Part 4: Print the suitcolor, hascape, and motto for each hero in the hero ArrayList and capedheroes 2D array to verify their contents after completing Part 3 above. Sample output is shown below: Page 5

6 P7D. College Tuition! In this program, you will write an abstract class Student and three concrete classes, UnderGrad and Graduate (that inherit from Student ) and PostGraduate that inherits from Graduate. The requirements for each of the classes are shown below: Part 1: Write the class definition for the abstract class Student. The class definition should include private instance variables of type String to hold the student s first name, a String for his/her major and an int to hold the number of units taken. Getter and setter methods for each of the variables should be included in the class definition. It should also include an abstract method calculatetuition() as shown below: abstract public int calculatetuition(int units); Part 2: Write a three-argument constructor in the Student class to initialize each student s name, major, and number of units taken. Part 3: Write the class definitions for the UnderGrad, Graduate, and PostGraduate classes. These concrete classes should override the abstract method calculatetuition() according to the following rule: UnderGrad tuition is calculated by multiplying the number of units by $250. Graduate tuition is calculated by multiplying the number of units by $500. PostGraduate tuition is calculated by multiplying the number of units by $750. Part 4: Write a StudentDriver class to create two instances of each type of each concrete class, UnderGrad, Graduate, and PostGraduate. Add them to a 3x2 2D array named studentbody. Use a for or for-each loop to print each student s name and major along with the student s tuition based on the number of units the student is taking. Organize the Students in the 2D array as shown below: P7E. AP 2005 #2 Ticket Page 6

7 By the end of the lesson students should be able to: a. Write the Java code to allow class B inherit from class A. public class B extends A } b. Given a Java inheritance hierarchy, write the Java code to properly abstract out common class elements (instance variables and methods) into a superclass. c. Explain that only public data members and/or methods are inherited and that private data members and/or methods are not inherited. d. Describe the method call order in a Java inheritance hierarchy. e. Describe that class extension (inheritance) is different from class composition (building class from existing classes) and know when to use each technique. f. Write Java code to polymorphically process objects that exist in an inheritance hierarchy. g. Write Java methods that have polymorphic arguments and return types. h. Write the Java code to override an existing method. i. Write the Java code to overload an existing method. Page 7