For the questions below, consider the following class definition:
public class AClass
{
protected int x;
protected int y;
public AClass(int a, int b)
{
x = a;
y = b;
}
public int addEm( )
{
return x + y;
}
public void changeEm( )
{
x++;
y--;
}
public String toString( )
{
return "" + x + " " + y;
}
}
-You want addEm to now add all three values and return the sum and changeEm to change x and y, but leave z alone. Which should you do?
A) Redefine addEm and changeEm without referencing super.addEm( ) or super.changeEm( )
B) Redefine addEm to return the value of z + super.addEm( ), but leave changeEm alone
C) Redefine changeEm to call super.changeEm( ) and then set z = x + y, but leave addEm alone
D) Redefine addEm to return the value of z + super.addEm( ) and redefine changeEm to call super.changeEm( ) and then set z = x + y
E) Redefine changeEm to call super.changeEm( ) without doing anything to z, and redefine addEm to return super.addEm( )

Question

Quizplus · Accepted Answer

B) Since super.changeEm( ) will not affect z and we don't want changeEm to affect z, there is no need to redefine changeEm for BClass. Any reference to changeEm( ) will reference AClass'version which is the same one that BClass will use. But addEm needs redefining because the inherited method addEm calls AClass'addEm which only adds x and y together. Now, we want to add x, y and z together. We can either redefine addEm entirely, or use super.addEm( ) and add z to the value returned. The latter approach is better since it reuses previously written code.

For the Questions Below, Consider the Following Class Definition