package shapepkg;

public abstract class Shape implements Comparable {
   private String myName;

   public Shape (String shapeName ) {
      myName = shapeName;
   }

   abstract public double getArea( ); // Provided by sub-class

   public String getName() {
      return myName;
   }

   public String toString() {
      return "Name = " + myName + ", Area = " + getArea( );
   }

   public int compareTo (Object rhs) {
      if(getArea( ) < ((Shape)rhs).getArea())
         return -1;
      else if (getArea() > ((Shape)rhs).getArea())
         return 1;
      else
         return 0;
    }
}
========================================================================
package shapepkg;

public class Circle extends Shape {
    private double myRadius;

    public Circle(String name, double r) {
       super( name );
       myRadius = r;
    }

    public double getArea() {
        return Math.PI * myRadius * myRadius;
    }

    public double getRadius() {
       return myRadius;
    }

    public String toString() {
       return super.toString() + ", Radius: " + myRadius;
    }
}
========================================================================
package shapepkg;

public class Rectangle extends Shape {
    private double myLength;
    private double myWidth;

    public Rectangle(String name, double len, double wid) {
       super( name );
       myLength = len;
       myWidth = wid;
    }

    public double getArea() {
       return myLength * myWidth;
    }

    public double getLength() {
       return myLength;
    }

    public double getWidth() {
       return myWidth;
    }

    public String toString() {
       return super.toString() + ", Length = " +
           myLength + ", Width = " + myWidth;
    }
}
===============================================================
package shapepkg;

public class Square extends Rectangle {
    public Square(String name, double side) {
       super(name, side, side);
    }

    public double getSide() {
       return getLength();
    }

    public String toString() {
       return super.toString() +  ", Side = " + getSide();
    }
}
==============================================================
package shapepkg;

// Sorts.java: object insertion sort
public class Sorts {

   //  insertionSort: Sorts array of objects using the insertion sort
   public static void insertionSort (Comparable[] objects) {
      for (int index = 1; index < objects.length; index++) {
         Comparable key = objects[index];
         int position = index;
         // shift larger values to the right
         while (position > 0 && objects[position-1].compareTo(key) > 0) {
            objects[position] = objects[position-1];
            position--;
         }
         objects[position] = key;
      }
   }
}
================================================================
package shapepkg;

public class ShapeTest {

   public static void main(String[] args) {
      Shape[] myShapes = new Shape[5];
      myShapes[0] = new Circle("Circle", 3);
      myShapes[1] = new Rectangle("Rectangle", 3, 4);
      myShapes[2] = new Square("Square", 6);
      myShapes[3] = new Rectangle("Another Rectangle", 4, 5);
      myShapes[4] = new Circle("Circle", 5);
      System.out.println("Original array:");
      for (int k = 0; k < myShapes.length; k++)
         System.out.println(myShapes[k]);
      Sorts.insertionSort(myShapes);
      System.out.println("Sorted array:");
      for (int k = 0; k < myShapes.length; k++)
         System.out.println(myShapes[k]);
  }
}
================================================================
Run:

Original array:
Name = Circle, Area = 28.274333882308138, Radius: 3.0
Name = Rectangle, Area = 12.0, Length = 3.0, Width = 4.0
Name = Square, Area = 36.0, Length = 6.0, Width = 6.0, Side = 6.0
Name = Another Rectangle, Area = 20.0, Length = 4.0, Width = 5.0
Name = Circle, Area = 78.53981633974483, Radius: 5.0
Sorted array:
Name = Rectangle, Area = 12.0, Length = 3.0, Width = 4.0
Name = Another Rectangle, Area = 20.0, Length = 4.0, Width = 5.0
Name = Circle, Area = 28.274333882308138, Radius: 3.0
Name = Square, Area = 36.0, Length = 6.0, Width = 6.0, Side = 6.0
Name = Circle, Area = 78.53981633974483, Radius: 5.0
================================================================
Other integer sorts:

   // bubbleSort: keep exchanging any two elements not in order
   public static void bubbleSort (int[] numbers) {
      int temp;
      for (int dummy = 0; dummy < numbers.length - 1; dummy++) {
         for (int index = 1; index < numbers.length; index++) {
            if (numbers[index-1] > numbers[index]) {
               // Swap the values
               temp = numbers[index-1];
               numbers[index-1] = numbers[index];
               numbers[index] = temp;
            }
         }
      }
   }

   // selectionSort: keep selecting out the minimum value
   public static void selectionSort (int[] numbers) {
      int min, temp;

      for (int index = 0; index < numbers.length-1; index++) {
         min = index;
         for (int scan = index+1; scan < numbers.length; scan++)
            if (numbers[scan] < numbers[min])
               min = scan;

         // Swap the values
         temp = numbers[min];
         numbers[min] = numbers[index];
         numbers[index] = temp;
      }
   }