Question

This quiz uses the three classes below. Watch out for bugs! public class Trapezoid { private double height, width, base; public Trapezoid(double h, double w, double b) { setHeight(h); setWidth(w); setBase(b); } public double getHeight() { return height; } public double getWidth() { return width; } public double getBase() { return base; } public void setHeight(double h) { height = h; } public void setWidth(double w) { width = w; } public void setBase(double b) { base = b; } public double area() { return getHeight() * (getWidth() + getBase()) / 2; } public double perimeter() { return 2 * getHeight() + getWidth() + getBase(); } } public class Rectangle extends Trapezoid { public Rectangle(double h, double w) { super(h, w, w); } public double area() { return getHeight() * getWidth(); } } public class Square extends Rectangle { public Square(double w) { super(w, w); } public double area() { return getWidth() * getWidth(); } }

QUESTION 1

What is output by the following code?

Trapezoid t = new Trapezoid(2, 4, 6);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 2

What is output by the following code?

Rectangle r = new Rectangle(4, 6);
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 3

What is output by the following code?

Square s = new Square(6);
double a = s.area();
double p = s.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 4

What is output by the following code?

Trapezoid t = new Trapezoid(2, 4, 6);
t.setWidth(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 5

What is output by the following code?

Rectangle r = new Rectangle(4, 6);
r.setWidth(8);
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 6

What is output by the following code?

Square s = new Square(6);
s.setWidth(8);
double a = s.area();
double p = s.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 7

What is output by the following code?

Trapezoid t = new Trapezoid(2, 4, 6);
t.setHeight(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 8

What is output by the following code?

Rectangle r = new Rectangle(4, 6);
r.setHeight(8);
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 9

What is output by the following code?

Square s = new Square(6);
s.setHeight(8);
double a = s.area();
double p = s.perimeter();
System.out.print(a + " " + p);

5 points   

QUESTION 10

What is output by the following code?

Trapezoid t = new Trapezoid(2, 4, 6);
t.setBase(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

Answer 1

1)
Trapezoid t = new Trapezoid(2, 4, 6); //the obect for Trapezoid class is created and constuctor is invoked
double a = t.area();//return value of area method of Trapezoid class is stored in a
double p = t.perimeter();//return value of perimeter method of Trapezoid class is stored in p
System.out.print(a + " " + p); //a and p are printed

output:10.00 14.00
2)

Rectangle r = new Rectangle(4, 6);
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);

output: 24.00 20.00

3)

Square s = new Square(6);
double a = s.area();
double p = s.perimeter();
System.out.print(a + " " + p);

output: 36.0 24.0

4)Trapezoid t = new Trapezoid(2, 4, 6);
t.setWidth(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

output:- 14.0 18.0

5)
Rectangle r = new Rectangle(4, 6); //here the height will be set to 4 and both width and base will be set to 6
r.setWidth(8);//here only width willbe set to 8, leaving base as 6. so the result will not be as expected
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);
output: 32.0 22.0

6)Square s = new Square(6);//here height, width and base are all set to 6

s.setWidth(8); //only width changed to 8
double a = s.area(); //this uses only width so result is as expected.
double p = s.perimeter();// this uses all the three dimensions so result will not be as expected
System.out.print(a + " " + p);

output: 64.0 26.0

7)Trapezoid t = new Trapezoid(2, 4, 6);
t.setHeight(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);

output: 40.0 26.0

8)Rectangle r = new Rectangle(4, 6);
r.setHeight(8);
double a = r.area();
double p = r.perimeter();
System.out.print(a + " " + p);

output: 48.0 28.0

9)Square s = new Square(6);
s.setHeight(8);
double a = s.area();
double p = s.perimeter();
System.out.print(a + " " + p);

output:36.0 28.0

10)Trapezoid t = new Trapezoid(2, 4, 6);
t.setBase(8);
double a = t.area();
double p = t.perimeter();
System.out.print(a + " " + p);
output:12.0 16.0

• Here to eliminate unexpected results it is better to write separate perimeter functions as well for each class