This assignment demonstrates the use of interfaces and how they can be used in c

Question

This assignment demonstrates the use of interfaces and how they can be used in combination with inheritance.
Use the four shapes that you implemented in Assignment Inheritance as a starting point.
I recommend creating a copy before you implement any changes.
In this assignment you will create 2 interfaces: Shape and Printable and you will modify the classes Rectangle, Square,
IsoscelesRightTriangle, and Circle so that they implement one or both of the interfaces.
In addition you will create a class called InterfaceApp (different from InheritanceApp). This class includes the main
method and demonstrates the polymorphic behavior of interfaces.
Declare the interfaces according to the UML diagrams:
ad interface Shape:
perimeter .. returns the perimeter of the shape
area .. returns the area of the shape
ad interface Printable:
print

Explanation / Answer

interfaceApp.java

import java.lang.*;
interface Shape{
double perimeter();
double area();
}
interface Printable{
void print();
}
class Rectangle implements Shape, Printable
{
   int len,bre,peri,are;
   Rectangle(int l,int b){
       len = l;
       bre = b;
   }
   public double perimeter()
   {
       return len * bre;
   }
   public double area(){
       return len * bre;
   }
   public void print()
   {
       for(int i=0;i<bre;i++){
           if(i==0 || i==bre-1){
           for(int j=0;j<len;j++){
               System.out.print("* ");
           }
           }
           else{
               System.out.print("*");
               for(int k=0;k<len-1;k++)System.out.print(" ");
               System.out.print("*");
           }
           System.out.print(" ");
           }
       }
   public String toString(){
       return "Rectangle(6X3)";
   }
}
class Square implements Shape, Printable
{
   int len,peri,are;
   public Square(int l){
       len = l;
   }
   public double perimeter()
   {
       return len * len;
   }
   public double area(){
       return len * len;
   }
   public void print()
   {
       for(int i=0;i<len;i++){
           if(i==0 || i==len-1){
           for(int j=0;j<len;j++){
               System.out.print("* ");
           }
           }
           else{
               System.out.print("*");
               for(int k=0;k<len-1;k++)System.out.print(" ");
               System.out.print("*");
           }
           System.out.print(" ");
           }
   }
   public String toString(){
       return "Square(5)";
   }
}

class IsoscelesRightTriangle implements Shape, Printable
{
   int h;
   double peri,are;
   public IsoscelesRightTriangle(int he){
       h= he;
   }
   public double perimeter(){
       return h + h + Math.sqrt((6*6)+(6*6));
   }
   public double area()
   {
       return (double)(h*h)/2;
   }
   public void print(){
       for(int i=0;i<h;i++){
           for(int j=0;j<i;j++){
               System.out.print("* ");
           }
           System.out.print(" ");
       }
   }
   public String toString(){
       return "Triangle(6)";
   }
}
class Circle implements Shape
{
   int r,dia;
   double peri,are;
   public Circle(int rad){
       r = rad;
   }
   public double perimeter(){
       return 2 * 3.14 * r;
   }
   public double area(){
       return 3.14 * r * r;
   }
   public double diameter(){
       return r * 2;
   }
   public String toString(){
       return "Circle(5)";
   }
}
public class InterfaceApp {
   public static void main(String[] args) {
       Shape []sh = new Shape[3];
       Printable []p = new Printable[3];
       Rectangle rect = new Rectangle(6, 3);
       Square squ = new Square(5);
       IsoscelesRightTriangle is = new IsoscelesRightTriangle(6);
       Circle cir = new Circle(5);
       System.out.println("Diameter:"+cir.diameter()+" Perimeter:"+cir.perimeter()+" Area:"+cir.area());
       System.out.println(cir);
       System.out.print("Shape Array: -------- ");
       sh[0] = squ;
       sh[1] = rect;
       sh[2] = is;
       p[0] = squ;
       p[1] = rect;
       p[2] = is;
       for(int i=0;i<sh.length;i++){
           System.out.println(sh[i]+" Perimeter:"+sh[i].perimeter()+" Area:"+sh[i].area());
           if(p[i] instanceof Printable){
               p[i].print();
           }
       }
      
   }
}

output:

Diameter:10.0
Perimeter:31.400000000000002
Area:78.5
Circle(5)
Shape Array:
--------
Square(5)
Perimeter:25.0
Area:25.0
* * * * *
* *
* *
* *
* * * * *
Rectangle(6X3)
Perimeter:18.0
Area:18.0
* * * * * *
* *
* * * * * *
Triangle(6)
Perimeter:20.485281374238568
Area:18.0

*
* *
* * *
* * * *
* * * * *

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