APCS Unit 5 Exam. Assuming all four classes have a default constructor, which of the following statements would result in an error from the compiler?

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Lindsey Erica Benson
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1 APCS Unit 5 Exam Name 1. Suppose we had a superclass called Fruit. The subclasses of this superclass are Apple, Orange, and Banana. Consider the following reference variable declarations. Fruit f; Banana b; Orange oj; Apple a; Assuming all four classes have a default constructor, which of the following statements would result in an error from the compiler? f = new Fruit( ); b = new Fruit( ); f = new Apple( ); oj = new Banana( ); Ok NOT Ok NOT 2. Give one difference between an interface and an abstract class. (Other than one is an interface and the other is a class.) An abstract class can define instance variables, an interface may only contain method headers and/or class constants. What is one way they are the same? Both can require behaviors of their extending/implementing classes.

2 3. Consider the following partial class declaration. public class Person private String name; private int height; // assume given in total inches private int age; public Person ( String n, int h, int a ) // constructor implementation and other methods not shown. 4, Write the implementation of a compareto method for this class. A Person object will be deemed greater than if they are taller, equal if they are the same height, or less than otherwise. public int CompareTo ( Object obj ) return height ((Person)obj).height; 5. Write a clone method for this class. public Object clone ( ) return new Person( name, height, age);

3 6. Suppose we had the following method. public static double gethypotenuse ( int leg1, int leg2 ) if( leg1 <= 0 leg2 <= 0 ) throw new IllegalArgumentException ( Both dimensions must be positive. ); return Math.sqrt( leg1*leg1 + leg2*leg2); Show a call to this method so that if the exception is thrown, it will be caught and the message will be displayed. You may assume the following integer declarations and that they have been given values prior to your code. int x, y; try double h = gethypotenuse( x, y ); catch( IllegalArgumentException e ) System.out.println( e ) ; 7. Suppose we had a super class called Fish. This class had three sub-classes, Shark, Bass, and Minnow. Show the declaration for an array of size 20 that could hold an object of all three of the given sub-types. This would be in a client program. Fish [ ] tank = new Fish[ 20 ];

4 8. Given the class structure in question #7, assume that only the Shark class has a method called bite( ). This method requires no parameters and does not return a value. Using a for loop, show how you could traverse the array you declared in question #7 and call the bite( ) method for any Shark objects that are present. You may assume the array is full, but that it contains at least one of each of the sub-types. This code would appear in a client. for( int x = 0; x<tank.length; x++ ) if( tank[x] instanceof Shark ) ((Shark)tank[x]).bite( ); = For the remaining questions on the exam use the handout provided. 9. In order to compile, the Pizza class will have to define the method addon. This method will check the number of toppings for the given pizza object. If the number exceeds 2, the method will add on $1.75 for each additional topping to the price. Write the full implementation of this instance method in the Pizza class. public void addon ( ) if( numberoftoppings > 2 ) price += (numberoftoppings 2 ) * 1.75;

5 10. Show the declaration of an array that could hold up to 50 Pizza or Salad objects. This code would be in a client program. Lunch [ ] food = new Lunch[50]; 11. Write a static method for a client file that would take the array you declared in #10 as a parameter. This method would find the total cost of all items in the list. You may not assume the array is full. public static double totalcost( Lunch [ ] list ) double total = 0; for( int x=0; x < list.length; x++ ) if( list[x]!= null ) return total; total += list[x].getprice( ); 12. Write a static method that would take the array you declared in #10 as a parameter. The method will find and return the average weight of all the Salad objects in the list. You may not assume the array is full. public static double getavgsal ( Lunch [ ] list ) double total = 0; int i = 0; for( int x=0; x<list.length; x++ ) if( list[x]!= null && list[x] instanceof Salad ) total += ((Salad)list[x].getWeight( );

6 i++; return total / i;

Full file at Chapter 2 - Inheritance and Exception Handling

Full file at Chapter 2 - Inheritance and Exception Handling Chapter 2 - Inheritance and Exception Handling TRUE/FALSE 1. The superclass inherits all its properties from the subclass. ANS: F PTS: 1 REF: 76 2. Private members of a superclass can be accessed by a