Deteksi tumbukan dengan javaFX

Pada tutorial ini saya akan memberikan  bagaimana cara mendeteksti tumbukan dengan javaFX yang previewnya dapat dilihat pada gambar berikut:

Adapaun source codenya adalah:

package fjr.collision;

import java.util.Random;

import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBuilder;
import javafx.scene.shape.Circle;
import javafx.scene.shape.CircleBuilder;
import javafx.stage.Stage;

public class TestCollision extends Application {

 double r = 14.0;
 Random rand = new Random();

 double xwidth = 400;
 double ywidth = 400;

 int numberParticle = 100;

 // uji tumbukan
 public boolean testCol(Circle p1, Circle p2) {
  double dx = p1.getCenterX() - p2.getCenterX();
  double dy = p1.getCenterY() - p2.getCenterY();
  if (dx * dx + dy * dy < 4 * r * r) {
   return true;
  }
  return false;
 }

 public void removeOverlap(ObservableList list) {
  for (int i = 0 ; i< list.size() ; i++ ) {
   if (list.get(i) instanceof Circle) {
    Circle p1 = (Circle) list.get(i);
    for (int j = list.size()- 1 ; j   > i ; j-- ) {
     if (list.get(j) instanceof Circle) {
      Circle p2 = (Circle) list.get(j);
      if (testCol(p1, p2)) {
       list.remove(j);
      }
     }
    }
   }
  }
 }

 public static void main(String[] args) {
  launch(args);
 }

 Button button, button1;
 boolean state = true;

 @Override
 public void start(Stage primaryStage) throws Exception {

  final Group root = new Group();
  primaryStage.setScene(new Scene(root, xwidth, ywidth));

  for (int i = 0; i < numberParticle; i++) {
   root.getChildren().add(
     CircleBuilder.create().centerX(rand.nextDouble() * xwidth)
       .centerY(rand.nextDouble() * ywidth).radius(r)
       .build());
  }

  button = ButtonBuilder.create().text("ORGANIZE").translateX(10)
    .translateY(10).build();
  button1 = ButtonBuilder.create().text("RESET").translateX(100)
    .translateY(10).build();

  root.getChildren().addAll(button, button1);

  button.setOnAction(new EventHandler() {

   @Override
   public void handle(ActionEvent arg0) {
    if (state) {
     removeOverlap(root.getChildren());
    }
    state = false;
   }
  });

  button1.setOnAction(new EventHandler() {

   @Override
   public void handle(ActionEvent arg0) {
    for (int i = root.getChildren().size() - 1; i >= 0; i--) {
     root.getChildren().remove(i);
    }

    for (int i = 0; i < numberParticle; i++) {
     root.getChildren().add(
       CircleBuilder.create()
         .centerX(rand.nextDouble() * xwidth)
         .centerY(rand.nextDouble() * ywidth)
         .radius(r).build());
    }
    root.getChildren().addAll(button, button1);
    state = true;
   }
  });

  primaryStage.show();

 }
}