COP3330.01, Fall 2001
S. Lang Solution Key to Test #2 (11/07/2001)
1. (30 pts.) Multiple Choice questions. Select the answers from the list following this problem,
and place the numerical label next to the answer into the blank space of the questions. Note
that an answer from the answer list may be used multiple times (or zero times).
(a) The situation of methods (or constructors) within a class hierarchy that use the same
name but have different parameters is overloading.
(b) The constructor of an extended class uses the method name super to invoke the
constructor of its base class.
(c) When assigning an object of a supertype to a reference of a subtype, cast is needed to
avoid the compile-time error.
(d) An interface can extends other interface or interfaces.
(e) When splitting a class into an interface and an implementation, instance variable of the
class cannot be kept in the interface.
Answer questions (f) (j) based on the Java code in the code box below:
(f) How is method m1( ) of class B related to method m1( ) of class A overloading
(g) How is instance variable double x of class B related to int x of class A hiding
(h) In class C, how is method m2( ) of class A related to method m2( ) of interface K nothing
(i) How is method m1( ) implemented in class C inherits
(j) How is method m2( ) of class B related to method m2( ) of class A overriding
Answer List (1 –15): Java code for Questions (f) (j):
1. hiding
2. overloading
3. overriding
4. compile-time error
5. super
6. instance variable
7. method
8. static constant
9. this
10. cast
11. collapsing
12. implements
13. extends
14. inherits
15. nothing
interface K {
void m1( );
int m2( );
}
class A {
public void m1( ) { …}
public void m2( ) { …}
protected int x;
}
class B extends A {
public void m1(int x) { …}
public void m2( ) { …}
protected double x;
}
class C extends B implements K {
….
}
