small improvements on tutorial 5

T5Q3/src/Polygon.java

@@ -1,5 +1,5 @@
-public abstract class Polygon {
+//public abstract class Polygon {
-//public class Polygon {
+public class Polygon {
     public enum KindofPolygon {
         POLY_PLAIN,
         POLY_RECT,
@@ -29,14 +29,45 @@ public abstract class Polygon {
         return name;
     }
 
-//    public float calArea() {
+    public float calArea() {
-//        return 0;
+        return 0;
-//    }
+    }
 
     public void printWidthHeight( ) {
         System.out.println("Width = " + width + " Height = " + height);
     }
 
-    public abstract float calArea();
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 }

T5Q3/src/TestPolygon.java

@@ -38,6 +38,25 @@ public class TestPolygon {
 
 
 
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     public static void printArea(Polygon poly) {
@@ -48,11 +67,11 @@ public class TestPolygon {
     public static void main2(String[] args ) {
 
         Rectangle rect = new Rectangle("Rectangle", 3.0f, 4.0f);
-        printArea(rect);
+        printArea(rect); // dynamic binding
         rect.printWidthHeight();
 
         Triangle triangle= new Triangle("Triangle", 3.0f, 4.0f);
-        printArea(triangle);
+        printArea(triangle); // dynamic binding
         triangle.printWidthHeight();
     }
 }