Shape.java

public class Shape{
   private String name;

   public Shape(String n){
      name = n;
   }

   public String getName(){
      return name;
   }

   public double area(){
      return 0.0;
   }

   public double perimeter(){
      return 0.0;
   }

   public String toString(){
      return "Shape";
   }
}

class Polygon extends Shape{
   private int numSides;

   public Polygon(String n, int ns){
      super(n);
      numSides = ns;
   }

   public String toString(){
      return "Polygon with " + numSides + " sides";
   }
}

class Triangle extends Polygon{
   private double leg1, leg2;

   public Triangle(double l1, double l2){
      super("Triangle", 3);
      leg1 = l1;
      leg2 = l2;
   }

   public double hypotenuse(){
      return Math.sqrt( Math.pow(leg1, 2) + Math.pow(leg2, 2) );
   }

   public double perimeter(){
      return leg1 + leg2 + hypotenuse();
   }

   public double area(){
      double s = perimeter() / 2;
      return Math.sqrt( s * (s - leg1) * (s - leg2) * (s - hypotenuse()) );
   }

   public String toString(){
      return super.toString() + "\n" + getName() + " with legs of length " + leg1 + " and " + leg2;
   }
}