1. m/c 6-10 t/f 6-10 AP free style s/a 7.6-7.7
Chapter 7 answers
m/c 6-10
t/f 6-10
AP free style
s/a

2. Multiple choice 6 Give classes A and B what will print for
Class A{void foo(){ prints “A’s foo”}
Class B extends A {void foo() {prints “B’s foo”}
A aRef = new B();
aRef.foo(); b

3. Given Object obj = new String(“hello”); which will NOT cause a compile error?
obj.toUpperCase();
obj.substring(0,5);
obj.equals(“hi”);
obj.compareTo(“hi”);
All of them will cause a compile error c

4. 8. Given void doSomething(Object param) which is NOT a valid call?
doSomething(“Java”);
doSomething(new String(“Java”);
doSomething(14);
doSomething(new Integer(14));
All are valid calls
C according to the book but they are wrong because of autoboxing which changes the int in c to an Integer object

5. 9 b

6. 10 e

7. True/False A class can be both a superclass and a subclass
All classes are derived from the Object class
An abstract class cannot be instantiated
A polymorphic reference variable can point to different types of objects at different times
Polymorphism may occur with inheritance but not with interfaces F

8. AP Multiple Choice
6. A
In warmup file

9. See BlueJ for short answer 7.6 traffic light and 7.7 rubber circle

10. AP-Style Free Response Solution
public class Perishable extends InventoryItem {
private Date expiration;
private static final double DISCOUNT = 0.01;
public Perishable (Date entry, double price, Date expirationDate)
super (entry, price);
expiration = expirationDate; }
public double getPrice()
if (expiration.compareTo(getEntryDate()) < 0)
return getBasePrice() * DISCOUNT;
else
return getBasePrice(); b.
public ArrayList<InventoryItem> getItems (double loPrice, double hiPrice)
ArrayList<InventoryItem> list = new ArrayList<InventoryItem>();
for (InventoryItem ii : items)
if ((ii.getPrice() >= loPrice) && (ii.getPrice() <= hiPrice))
list.add(ii);
return list;