Thread: Help me please with Shape hierarchy

I am having trouble with this code for my Java class, I can not get this to work in the Myprogramming lab, it seemed to be an issue with the prompt. Here is the damage I have done thus far and thanks!:


Driver.java:32: error: non-static variable this cannot be referenced from a static context
obj = new Circle(r);
^
Driver.java:38: error: non-static variable this cannot be referenced from a static context
obj = new Square(r);
^
Driver.java:48: error: non-static variable this cannot be referenced from a static context
obj = new Triangle(side1, side2, side3);
^
Driver.java:54: error: non-static variable this cannot be referenced from a static context
obj = new Sphere(r);
^
Driver.java:60: error: non-static variable this cannot be referenced from a static context
obj = new Cube(r);
^
Driver.java:66: error: non-static variable this cannot be referenced from a static context
obj = new Tetrahedron(r);
^
6 errors
1 import java.util.Scanner;
2
3 class Driver
4 {
5
6
7 private static void main(String[] args)
8 {
9 Object obj;
10 int first;
11 int second;
12 double r;
13 Scanner stdin = new Scanner(System.in);
14 System.out.print("Enter\n1)Two dimensional shape\n2)Three dimensional shape:");
15 first = stdin.nextInt();
16 if(first==1)
17
18 {
19 System.out.print("Enter\n1)Circle\n2)Square\n3)Tri angle:");
20 second = stdin.nextInt();
21
22 } else {
23 System.out.print("Enter\n1)Sphere\n2)Cube\n3)Tetra hedron:");
24 second = stdin.nextInt();
25 }
26 int choice = first*10 + second;
27 switch(choice)
28 {
29 case 11:
30 System.out.print("Enter radius of circle:");
31 r = stdin.nextDouble();
32 obj = new Circle(r);
33 System.out.print(obj.toString());
34 break;
35 case 12:
36 System.out.print("Enter side of square:");
37 r = stdin.nextDouble();
38 obj = new Square(r);
39 System.out.print(obj.toString());
40 break;
41 case 13:
42 System.out.print("Enter side of triangle:");
43 double side1 = stdin.nextDouble();
44 System.out.print("Enter side of triangle:");
45 double side2 = stdin.nextDouble();
46 System.out.print("Enter side of triangle:");
47 double side3 = stdin.nextDouble();
48 obj = new Triangle(side1, side2, side3);
49 System.out.print(obj.toString());
50 break;
51 case 21:
52 System.out.print("Enter side of sphere");
53 r = stdin.nextDouble();
54 obj = new Sphere(r);
55 System.out.print(obj.toString());
56 break;
57 case 22:
58 System.out.print("Enter side of cube:");
59 r = stdin.nextDouble();
60 obj = new Cube(r);
61 System.out.print(obj.toString());
62 break;
63 case 23:
64 System.out.print("Enter side of tetrahedron:");
65 r = stdin.nextDouble();
66 obj = new Tetrahedron(r);
67 System.out.print(obj.toString());
68 break;
69 default:
70 System.out.print("NOPE");
71 break;
72
73
74
75
76
77
78
79 }
80
81 }
82
83 abstract class Shape extends Object {}
84 abstract class TwoDimensionalShape extends Shape
85 {
86 public double perimeter () {return 0.0;}
87 public double area() {return 0.0;}
88 public String toString()
89 {
90 return String.format("Area: %.2f%nPerimeter: %.2f%n", area(), perimeter ());
91 }
92 }
93 class Circle extends TwoDimensionalShape
94 {
95 private double r;
96 public Circle(double r) {this.r = r;}
97 public double area() {return Math.PI*this.r*this.r;}
98 public double perimeter() {return Math.PI * 2 * this.r;}
99
100 }
101
102 class Square extends TwoDimensionalShape
103 {
104 private double side;
105 public Square(double side) {this.side = side;}
106 public double area() {return this.side * this.side;}
107 public double perimeter() {return this.side * 4;}
108 }
109
110 class Triangle extends TwoDimensionalShape
111 {
112 private double side1;
113 private double side2;
114 private double side3;
115 public Triangle(double side1, double side2, double side3)
116 {
117 this.side1 = side1;
118 this.side2 = side2;
119 this.side3 = side3;
120 }
121 public double perimeter() {return this.side1 + this.side2 + this.side3;}
122 public double area()
123 {
124 double half = (this.side1+this.side2+this.side3)/2;
125 double calc = Math.sqrt(half*(half-this.side1)*(half-this.side2)*(half-this.side3));
126 return calc;
127 }
128 }
129
130 class ThreeDimensionalShape extends Shape
131 {
132 public double getVolume() {return 0.0;}
133 public double getSurfaceArea() {return 0.0;}
134 public String toString()
135 {
136 return String.format("Surface area:%.2f%nVolume: %.2f%n", getSurfaceArea(), getVolume());
137 }
138
139
140 }
141
142 class Sphere extends ThreeDimensionalShape
143 {
144 private double r;
145 public Sphere(double r) {this.r = r;}
146 public double getVolume() {return (Math.PI * this.r * this.r * this.r * 4)/3.0;}
147 public double getSurfaceArea() {return 4*Math.PI * this.r * this.r;}
148
149 }
150
151 class Cube extends ThreeDimensionalShape
152 {
153 private double side;
154 public Cube(double side) {this.side = side;}
155 public double getVolume() {return this.side * this.side * this.side;}
156 public double getSurfaceArea() {return this.side*this.side*6;}
157
158 }
159
160 class Tetrahedron extends ThreeDimensionalShape
161 {
162 private double side;
163 public Tetrahedron(double side) {this.side = side;}
164 public double getVolume() {return this.side * this.side * this.side/(Math.sqrt(2)*6);}
165 public double getSurfaceArea() {return this.side * this.side * Math.sqrt(3);}
166 }
167 }

Originally Posted by Norm

The non static inner classes can only be created in an instance of their enclosing class.
It should compile if the classes are changed to static by adding the keyword static before the keyword class:
static class Circle ...

That does work but then I get this error when I do this:

Driver.java:96: error: no enclosing instance of type Driver is in scope
public Circle(double r) {this.r = r;}
^
1 import java.util.Scanner;
2
3 class Driver
4 {
5
6
7 private static void main(String[] args)
8 {
9 Object obj;
10 int first;
11 int second;
12 double r;
13 Scanner stdin = new Scanner(System.in);
14 System.out.print("Enter\n1)Two dimensional shape\n2)Three dimensional shape:");
15 first = stdin.nextInt();
16 if(first==1)
17
18 {
19 System.out.print("Enter\n1)Circle\n2)Square\n3)Tri angle:");
20 second = stdin.nextInt();
21
22 } else {
23 System.out.print("Enter\n1)Sphere\n2)Cube\n3)Tetra hedron:");
24 second = stdin.nextInt();
25 }
26 int choice = first*10 + second;
27 switch(choice)
28 {
29 case 11:
30 System.out.print("Enter radius of circle:");
31 r = stdin.nextDouble();
32 obj = new Circle(r);
33 System.out.print(obj.toString());
34 break;
35 case 12:
36 System.out.print("Enter side of square:");
37 r = stdin.nextDouble();
38 obj = new Square(r);
39 System.out.print(obj.toString());
40 break;
41 case 13:
42 System.out.print("Enter side of triangle:");
43 double side1 = stdin.nextDouble();
44 System.out.print("Enter side of triangle:");
45 double side2 = stdin.nextDouble();
46 System.out.print("Enter side of triangle:");
47 double side3 = stdin.nextDouble();
48 obj = new Triangle(side1, side2, side3);
49 System.out.print(obj.toString());
50 break;
51 case 21:
52 System.out.print("Enter side of sphere");
53 r = stdin.nextDouble();
54 obj = new Sphere(r);
55 System.out.print(obj.toString());
56 break;
57 case 22:
58 System.out.print("Enter side of cube:");
59 r = stdin.nextDouble();
60 obj = new Cube(r);
61 System.out.print(obj.toString());
62 break;
63 case 23:
64 System.out.print("Enter side of tetrahedron:");
65 r = stdin.nextDouble();
66 obj = new Tetrahedron(r);
67 System.out.print(obj.toString());
68 break;
69 default:
70 System.out.print("NOPE");
71 break;
72
73
74
75
76
77
78
79 }
80
81 }
82
83 abstract class Shape extends Object {}
84 abstract class TwoDimensionalShape extends Shape
85 {
86 public double perimeter () {return 0.0;}
87 public double area() {return 0.0;}
88 public String toString()
89 {
90 return String.format("Area: %.2f%nPerimeter: %.2f%n", area(), perimeter ());
91 }
92 }
93 static class Circle extends TwoDimensionalShape
94 {
95 private double r;
96 public Circle(double r) {this.r = r;}
97 public double area() {return Math.PI*this.r*this.r;}
98 public double perimeter() {return Math.PI * 2 * this.r;}
99
100 }
101
102 static class Square extends TwoDimensionalShape
103 {
104 private double side;
105 public Square(double side) {this.side = side;}
106 public double area() {return this.side * this.side;}
107 public double perimeter() {return this.side * 4;}
108 }
109
110 static class Triangle extends TwoDimensionalShape
111 {
112 private double side1;
113 private double side2;
114 private double side3;
115 public Triangle(double side1, double side2, double side3)
116 {
117 this.side1 = side1;
118 this.side2 = side2;
119 this.side3 = side3;
120 }
121 public double perimeter() {return this.side1 + this.side2 + this.side3;}
122 public double area()
123 {
124 double half = (this.side1+this.side2+this.side3)/2;
125 double calc = Math.sqrt(half*(half-this.side1)*(half-this.side2)*(half-this.side3));
126 return calc;
127 }
128 }
129
130 static class ThreeDimensionalShape extends Shape
131 {
132 public double getVolume() {return 0.0;}
133 public double getSurfaceArea() {return 0.0;}
134 public String toString()
135 {
136 return String.format("Surface area:%.2f%nVolume: %.2f%n", getSurfaceArea(), getVolume());
137 }
138
139
140 }
141
142 static class Sphere extends ThreeDimensionalShape
143 {
144 private double r;
145 public Sphere(double r) {this.r = r;}
146 public double getVolume() {return (Math.PI * this.r * this.r * this.r * 4)/3.0;}
147 public double getSurfaceArea() {return 4*Math.PI * this.r * this.r;}
148
149 }
150
151 static class Cube extends ThreeDimensionalShape
152 {
153 private double side;
154 public Cube(double side) {this.side = side;}
155 public double getVolume() {return this.side * this.side * this.side;}
156 public double getSurfaceArea() {return this.side*this.side*6;}
157
158 }
159
160 static class Tetrahedron extends ThreeDimensionalShape
161 {
162 private double side;
163 public Tetrahedron(double side) {this.side = side;}
164 public double getVolume() {return this.side * this.side * this.side/(Math.sqrt(2)*6);}
165 public double getSurfaceArea() {return this.side * this.side * Math.sqrt(3);}
166 }
167 }

Originally Posted by Norm

What program does that message come from?


Can you follow that program's suggestions to change your code to satisfy that program?

Also try executing the program using the java command so you can see what the code does when its executed.

I changed it from private static void to public static void and the myprpgramminglab is at least prompting

Sorry I thought I responded, I figured it out, thank you so much for your help Norm!