Add Ex 18.19

Author: jsquared21

Diff for: Exercise_18/Exercise_18_19/Exercise_18_19$SierpinskiTrianglePane.class

@@ -0,0 +1,110 @@
+/*********************************************************************************
+* (Sierpinski triangle) Revise Listing 18.9 to develop a program that lets the   *
+* user use the + and – buttons to increase or decrease the current order by 1,   *
+* as shown in Figure 18.12a. The initial order is 0. If the current order is 0,  *
+* the Decrease button is ignored.                                                *
+*********************************************************************************/
+import javafx.application.Application;
+import javafx.geometry.Point2D;
+import javafx.geometry.Pos;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.layout.BorderPane;
+import javafx.scene.layout.HBox;
+import javafx.scene.layout.Pane;
+import javafx.scene.paint.Color;
+import javafx.scene.shape.Polygon;
+import javafx.stage.Stage;
+
+public class Exercise_18_19 extends Application {
+	@Override // Override the start method in the Application class
+	public void start(Stage primaryStage) {
+		SierpinskiTrianglePane trianglePane = new SierpinskiTrianglePane();
+
+		// Create to buttons
+		Button btDecrease = new Button("-");
+		Button btIncrease = new Button("+");
+
+		// Create an register the handlers
+		btDecrease.setOnAction(e -> {
+			if (trianglePane.getOrder() > 0)
+				trianglePane.setOrder(trianglePane.getOrder() - 1);
+		});
+
+		btIncrease.setOnAction(
+			e -> trianglePane.setOrder(trianglePane.getOrder() + 1));
+		
+		// Pane to hold label, text field, and a button
+		HBox hBox = new HBox(10);
+		hBox.getChildren().addAll(btDecrease, btIncrease);
+		hBox.setAlignment(Pos.CENTER);
+
+		BorderPane borderPane = new BorderPane();
+		borderPane.setCenter(trianglePane);
+		borderPane.setBottom(hBox);
+
+		// Create a scene and place it in the stage
+		Scene scene = new Scene(borderPane, 200, 210);
+		primaryStage.setTitle("Exercise_18_19"); // Set the stage title
+		primaryStage.setScene(scene); // Place the scene in the stage
+		primaryStage.show(); // Display the stage
+
+		scene.widthProperty().addListener(ov -> trianglePane.paint());
+		scene.heightProperty().addListener(ov -> trianglePane.paint());
+	}
+
+	/** Pane for displaying triangles */
+	static class SierpinskiTrianglePane extends Pane {
+		private int order = 0;
+
+		/** Set a new order */
+		public void setOrder(int order) {
+			this.order = order;
+			paint();
+		}
+
+		/** Return the order */
+		public int getOrder() {
+			return order;
+		}
+
+		SierpinskiTrianglePane() {
+		}
+
+		protected void paint() {
+			// Select three points in proportion to the pane size
+			Point2D p1 = new Point2D(getWidth() / 2, 10);
+			Point2D p2 = new Point2D(10, getHeight() - 10);
+			Point2D p3 = new Point2D(getWidth() - 10, getHeight() - 10);
+
+			this.getChildren().clear(); // Clear the pane before redisplay
+
+			displayTriangles(order, p1, p2, p3);
+		}
+
+		private void displayTriangles(int order, Point2D p1,
+				Point2D p2, Point2D p3) {
+			if (order == 0) {
+				// Draw a triangle to connect three points
+				Polygon triangle = new Polygon();
+				triangle.getPoints().addAll(p1.getX(), p1.getY(), p2.getX(),
+					p2.getY(), p3.getX(), p3.getY());
+				triangle.setStroke(Color.BLACK);
+				triangle.setFill(Color.WHITE);
+
+				this.getChildren().add(triangle);
+			}
+			else {
+				//Get the midpoint on each edge in the triangle
+				Point2D p12= p1.midpoint(p2);
+				Point2D p23= p2.midpoint(p3);
+				Point2D p31= p3.midpoint(p1);
+
+				// Recursively display three triangles
+				displayTriangles(order - 1, p1, p12, p31);
+				displayTriangles(order - 1, p12, p2, p23);
+				displayTriangles(order - 1, p31, p23, p3);
+			}
+		}
+	}
+}