Add ch 15 solutions for ex 17, 18, 19.

ch_09/exercise09_06/StopWatch.java

@@ -48,14 +48,14 @@ public StopWatch() {
     /**
      * ■ A method named start() that resets the startTime to the current time.
      */
-    void start() {
+    public void start() {
         startTime = System.currentTimeMillis();
     }
 
     /**
      * ■ A method named stop() that sets the endTime to the current time.
      */
-    void stop() {
+    public void stop() {
         endTime = System.currentTimeMillis();
     }
 

ch_15/Exercise15_17.java

@@ -0,0 +1,149 @@
+package ch_15;
+
+import javafx.application.Application;
+import javafx.collections.ObservableList;
+import javafx.geometry.Insets;
+import javafx.scene.Node;
+import javafx.scene.Scene;
+import javafx.scene.control.Label;
+import javafx.scene.input.MouseButton;
+import javafx.scene.layout.Pane;
+import javafx.scene.layout.VBox;
+import javafx.scene.paint.Color;
+import javafx.scene.shape.Circle;
+import javafx.scene.shape.Rectangle;
+import javafx.stage.Stage;
+
+import java.util.ArrayList;
+
+/**
+ * **15.17 (Geometry: find the bounding rectangle) Write a program that enables the user
+ * to add and remove points in a two-dimensional plane dynamically, as shown
+ * in Figure 15.29a. A minimum bounding rectangle is updated as the points are
+ * added and removed. Assume that the radius of each point is 10 pixels
+ */
+public class Exercise15_17 extends javafx.application.Application {
+
+    Pane pane = new Pane();
+    ArrayList<Circle> points = new ArrayList<>();
+    static final int RADIUS = 10;
+    static final Color FILL_COLOR = Color.TRANSPARENT;
+    static final Color LINE_COLOR = Color.BLACK;
+
+    static final Label instructionsHeader = new Label("INSTRUCTION");
+    static final Label addInstruction = new Label("Add: Left Click");
+    static final Label removeInstruction = new Label("Remove: Right Click");
+
+    public static void main(String[] args) {
+        Application.launch(args);
+    }
+
+    @Override
+    public void start(Stage primaryStage) {
+        double width = 600;
+        double height = 400;
+        VBox instructionsBox = new VBox();
+        instructionsBox.setPadding(new Insets(5, 5, 5, 5));
+        instructionsBox.setStyle("-fx-border-color: black");
+
+
+        instructionsBox.getChildren().addAll(instructionsHeader, addInstruction, removeInstruction);
+        Pane infoPane = new Pane(instructionsBox);
+        infoPane.setPadding(new Insets(10, 10, 10, 10));
+
+        pane.getChildren().addAll(infoPane);
+        instructionsBox.setLayoutX(10);
+        instructionsBox.setLayoutY(10);
+
+        pane.setOnMouseClicked(e -> {
+            double x = e.getX();
+            double y = e.getY();
+            if (infoPane.contains(x, y)) return;
+
+            if (e.getButton() == MouseButton.PRIMARY) {
+                Circle c = drawPoint(x, y);
+                points.add(c);
+                pane.getChildren().add(c);
+                drawMinBoundingRec();
+
+            } else if (e.getButton() == MouseButton.SECONDARY) {
+                removePoint(x, y);
+                drawMinBoundingRec();
+
+            }
+
+        });
+
+        Scene scene = new Scene(pane, width, height);
+        primaryStage.setScene(scene);
+        primaryStage.setTitle("click to draw circle");
+        primaryStage.show();
+    }
+
+    private Circle drawPoint(double x, double y) {
+        Circle c = new Circle(x, y, RADIUS, FILL_COLOR);
+        c.setStroke(LINE_COLOR);
+        return c;
+    }
+
+    private void drawMinBoundingRec() {
+        clearCurrentRectangle();
+
+        if (points.isEmpty()) return;
+
+        Circle top = points.get(0);
+        Circle bottom = points.get(0);
+        Circle right = points.get(0);
+        Circle left = points.get(0);
+
+        for (Circle c : points) {
+            if (c.getCenterX() < left.getCenterX()) left = c;
+            if (c.getCenterX() > right.getCenterX()) right = c;
+            if (c.getCenterY() > bottom.getCenterY()) bottom = c;
+            if (c.getCenterY() < top.getCenterY()) top = c;
+        }
+        double width = right.getCenterX() - left.getCenterX() + top.getRadius() * 2;
+        double height = bottom.getCenterY() - top.getCenterY() + top.getRadius() * 2;
+        double centerX = (right.getCenterX() + left.getCenterX()) / 2;
+        double centerY = (top.getCenterY() + bottom.getCenterY()) / 2;
+
+        Rectangle rec = calculateRectangle(centerX, centerY, width, height);
+        pane.getChildren().add(rec);
+
+    }
+
+    Rectangle calculateRectangle(double centerX, double centerY, double width, double height) {
+        Rectangle rec = new Rectangle(centerX - width / 2, centerY - height / 2, width, height);
+        rec.setStroke(LINE_COLOR);
+        rec.setFill(FILL_COLOR);
+        return rec;
+    }
+
+
+    private void removePoint(double x, double y) {
+        ObservableList<Node> list = pane.getChildren();
+        for (int i = list.size() - 1; i >= 0; i--) {
+            Node c = list.get(i);
+
+            if (c instanceof Circle && c.contains(x, y)) {
+                pane.getChildren().remove(c);
+                points.remove(c);
+
+                break;
+            }
+        }
+    }
+
+    private void clearCurrentRectangle() {
+        ObservableList<Node> list = pane.getChildren();
+
+        for (Node c : list) {
+            if (c instanceof Rectangle) {
+                pane.getChildren().remove(c);
+
+                break;
+            }
+        }
+
+    }
+}

ch_15/Exercise15_18.java

@@ -0,0 +1,46 @@
+package ch_15;
+
+import javafx.application.Application;
+import javafx.scene.Scene;
+import javafx.scene.layout.Pane;
+import javafx.scene.paint.Color;
+import javafx.scene.shape.Rectangle;
+import javafx.stage.Stage;
+
+/**
+ * **15.18 (Move a rectangle using mouse) Write a program that displays a rectangle.
+ * You can point the mouse inside the rectangle and drag (i.e., move with mouse
+ * pressed) the rectangle wherever the mouse goes. The mouse point becomes the
+ * center of the rectangle.
+ */
+public class Exercise15_18 extends javafx.application.Application {
+    static final double WIDTH = 600;
+    static final double HEIGHT = 600;
+    static final Color FILL_COLOR = Color.TRANSPARENT;
+    static final Color STROKE_COLOR = Color.BLACK;
+
+    public static void main(String[] args) {
+        Application.launch(args);
+    }
+
+    @Override
+    public void start(Stage primaryStage) {
+        Rectangle rec = rectangle();
+        Pane pane = new Pane(rec);
+        rec.setOnMouseDragged(e -> {
+            rec.setX(e.getX() - rec.getWidth() / 2);
+            rec.setY(e.getY() - rec.getHeight() / 2);
+        });
+        primaryStage.setScene(new Scene(pane, WIDTH, HEIGHT));
+        primaryStage.setTitle("Move a rectangle using mouse");
+        primaryStage.show();
+    }
+
+    Rectangle rectangle() {
+        Rectangle rec = new Rectangle(WIDTH / 2, HEIGHT / 2, 60, 30);
+        rec.setFill(FILL_COLOR);
+        rec.setStroke(STROKE_COLOR);
+        return rec;
+    }
+
+}

ch_15/Exercise15_19.java

@@ -0,0 +1,70 @@
+package ch_15;
+
+import ch_09.exercise09_06.StopWatch;
+import javafx.application.Application;
+import javafx.scene.Scene;
+import javafx.scene.layout.Pane;
+import javafx.scene.paint.Color;
+import javafx.scene.shape.Circle;
+import javafx.scene.text.Text;
+import javafx.stage.Stage;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * **15.19 (Game: eye-hand coordination) Write a program that displays a circle of radius
+ * 10 pixels filled with a random color at a random location on a pane, as shown
+ * in Figure 15.29b. When you click the circle, it disappears and a new random color
+ * circle is displayed at another random location. After twenty circles are
+ * clicked, display the time spent in the pane, as shown in Figure 15.29c
+ */
+public class Exercise15_19 extends javafx.application.Application {
+    private final double WIDTH = 600;
+    private final double HEIGHT = 600;
+    static final int MAX_CIRCLE_COUNT = 20;
+    static final String TITLE_TEXT = "Exercise15_19";
+
+    public static void main(String[] args) {
+        Application.launch(args);
+    }
+
+    @Override
+    public void start(Stage primaryStage) {
+        AtomicInteger circleCount = new AtomicInteger();
+        Circle circle = new Circle(0, 0, 10);
+        drawCircle(circle);
+        Pane pane = new Pane(circle);
+        Text countText = new Text(50, 50, String.valueOf(circleCount));
+        pane.getChildren().add(countText);
+        StopWatch stopWatch = new StopWatch();
+        circle.setOnMouseClicked(e -> {
+            int currentCount = circleCount.get();
+            if (currentCount == 0) {
+                stopWatch.start();
+            } else if (currentCount < MAX_CIRCLE_COUNT - 1) {
+                circleCount.getAndIncrement();
+                countText.setText(String.valueOf(circleCount));
+                drawCircle(circle);
+            } else {
+                stopWatch.stop();
+                circleCount.getAndIncrement();
+                countText.setText(String.valueOf(circleCount));
+                pane.getChildren().remove(circle);
+                pane.getChildren().add(new Text(WIDTH / 2, HEIGHT / 2, "Time spent is " +
+                        stopWatch.getElapsedTime() + " milliseconds"));
+            }
+        });
+        primaryStage.setScene(new Scene(pane, WIDTH, HEIGHT));
+        primaryStage.setTitle(TITLE_TEXT);
+        primaryStage.show();
+    }
+
+    private void drawCircle(Circle circle) {
+        double min = circle.getRadius() + 5;
+        double max = WIDTH - circle.getRadius() - 5;
+        circle.setCenterX((Math.random() * (max - min) + min));
+        max = WIDTH - circle.getRadius() - 5;
+        circle.setCenterY((Math.random() * (max - min) + min));
+        circle.setFill(new Color(Math.random(), Math.random(), Math.random(), 1));
+    }
+}