Exception in Application Cunstructor - exception

Question

I want to write a code with javaFX (Snake game) but right now it's not complete yet because it doesn't consider game Over yet. I wrote this and it is not object oriented. When I sort it and try to make it object oriented, (exactly with last code that run correctly) it throws Exception in Application constructor.
the exception is :
Exception in Application constructor
Exception in thread "main" java.lang.NoSuchMethodException: Main_Snake.main([Ljava.lang.String;)
at java.lang.Class.getMethod(Class.java:1819)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:125)
Someone said me to add :
public static void main(String[] args) {
launch(args);
}
After adding that, I get a new Exception:
Exception in Application constructor
Exception in thread "main" java.lang.RuntimeException: Unable to construct Application instance: class Main_Snake
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:910)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$156(LauncherImpl.java:187)
at java.lang.Thread.run(Thread.java:747)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:426)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:822)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$176(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$174(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$175(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Caused by: java.lang.StackOverflowError
at javafx.scene.Node.setTreeVisible(Node.java:8028)
at javafx.scene.Node.updateTreeVisible(Node.java:8021)
at javafx.scene.Node.<init>(Node.java:2372)
at javafx.scene.canvas.Canvas.<init>(Canvas.java:100)
at Main_Snake.<init>(Main_Snake.java:30)
at Snake.<init>(Main_Snake.java:164)
Can someone check my code please?
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import java.util.ArrayList;
/**
* Created by Nadia on 1/5/2016.
*/
public class Main_Snake extends Application{
Canvas canvas = new Canvas(800, 600);
boolean goNorth = true, goSouth, goWest, goEast;
int x, y = 0; // marbut be apple
boolean j = false;
// int gm_ov = 0; // vase game over shodan
ArrayList<Integer> X = new ArrayList<Integer>();
ArrayList<Integer> Y = new ArrayList<>();
Snake snake = new Snake();
Apple apple = new Apple();
#Override
public void start(Stage primaryStage) throws Exception {
BorderPane b = new BorderPane(canvas);
Scene scene = new Scene(b, 800, 600);
primaryStage.setScene(scene);
primaryStage.show();
//KeyBoard(scene);
scene.setOnKeyPressed(new EventHandler<KeyEvent>() {
#Override
public void handle(KeyEvent e) {
switch (e.getText()) {
case "w":
if (!goSouth) {
goNorth = true;
goSouth = false;
goWest = false;
goEast = false;
}
break;
case "s":
if (!goNorth) {
goSouth = true;
goNorth = false;
goWest = false;
goEast = false;
}
break;
case "a":
if (!goEast) {
goWest = true;
goEast = false;
goSouth = false;
goNorth = false;
}
break;
case "d":
if (!goWest) {
goEast = true;
goWest = false;
goSouth = false;
goNorth = false;
}
break;
}
}
});
play(snake,apple);
}
public void play(Snake snake , Apple apple) {
AnimationTimer timer = new AnimationTimer() {
private long lastUpdate = 0;
#Override
public void handle(long now) {
if (now - lastUpdate >= 40_000_000) { // payin avordane sor#
snake.pos_S(); // har bar mar rasm mishe bad az move va ye sib ba X,Y khodesh rasm mishe tu tabe move dar morede tabe Point hast
apple.pos_A();
apple.random_Pos();
snake.Move(apple);
lastUpdate = now; // sor#
}
}
};
timer.start();
}
/* public void KeyBoard(Scene scene) {
}*/
}
class Apple extends Main_Snake {
public void random_Pos() {
if (j == false) { // ye sib bede ke ru mar nabashe ( rasmesh tu rasme )
do {
x = (int) (Math.random() * 790 + 1);
y = (int) (Math.random() * 590 + 1);
} while (X.indexOf(x) != -1 && Y.get(X.indexOf(x)) == y || x % 10 != 0 || y % 10 != 0);
/*
inja aval chek kardam tu araylist x hast ya na ag bud sharte aval ok hala sharte do ke tu Y ham mibinim tu hamun shomare khune
y barabare y mast ag bud pas ina bar ham montabeghan va sharte dovom ham ok . 2 sharte akhar ham vase ine ke mare ma faghat mazrab
haye 10 and pas ta vaghti in se shart bargharare jahayie ke ma nemikhaym va hey jaye dg mide
*/
j = true;
}
}
public void pos_A() {
GraphicsContext gc = canvas.getGraphicsContext2D();
gc.setFill(Color.BLACK);
gc.fillRect(x, y, 10, 10);
}
public void Point() {
if (X.get(0) == x && Y.get(0) == y) {
j = false;
}
}
}
class Snake extends Main_Snake {
Snake(){ //cunstructor
X.add(400);
Y.add(300);
X.add(400);
Y.add(310);
X.add(400);
Y.add(320);
X.add(400);
Y.add(330);
X.add(400);
Y.add(340);
}
public void pos_S(){
GraphicsContext gc = canvas.getGraphicsContext2D();
gc.setFill(Color.WHITE);
gc.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
gc.setFill(Color.BLACK);
// keshidane mar (body yeki ezafe tar az adade morabaA mide)
for (int i = X.size() - 1; i >= 0; i--)
gc.fillRect(X.get(i), Y.get(i), 10, 10);
}
public void Move(Apple apple){
int Px = X.get(X.size() - 1);
int Py = Y.get(Y.size() - 1);
for (int z = X.size() - 1 ; z > 0 ; z--){
X.remove(z);
X.add(z , X.get(z-1) ) ;
Y.remove(z);
Y.add(z , Y.get(z-1) ) ;
}
if (goNorth) {
Y.add(0 , Y.get(0) - 10);
Y.remove(1);
}
if (goSouth) {
Y.add(0 , Y.get(0) + 10);
Y.remove(1);
}
if (goEast) {
X.add(0 , X.get(0) + 10);
X.remove(1);
}
if (goWest) {
X.add(0 , X.get(0) - 10);
X.remove(1);
}
apple.Point(); // emtiaz gerefte
if ( j == false) {
X.add(Px);
Y.add(Py);
}
if ( X.get(0) > 790 ){
X.remove(0);
X.add(0 , 0);
}
if ( X.get(0) < 0 ){
X.remove(0);
X.add(0 , 800);
}
if ( Y.get(0) > 590 ){
Y.remove(0);
Y.add(0 , 0);
}
if ( Y.get(0) < 0 ){
Y.remove(0);
Y.add(0 , 600);
}
}
}

Answer 1

When you start the application, it creates an instance of Main_Snake (since that is the Application class.
Your Main_Snake class has a field (instance variable) called snake of type Snake, which is initialized inline to a new Snake instance:
public class Main_Snake extends Application {
Snake snake = new Snake();
// ...
}
Your Snake class is a subclass of Main_Snake (why?):
public class Snake extends Main_Snake { ... }
This means it inherits all the fields and methods of Main_Snake. So when you create a new Snake instance, it initializes all the fields defined in Snake, as well as all the fields inherited from Main_Snake. In particular, it creates a new object called snake of type Snake (since that field is defined in the superclassMain_Snake).
So, so far we have:
JavaFX creates a Main_Snake at startup. As part of the process of creating Main_Snake, a Snake is created (since Main_Snake has a Snake).
As part of the process of creating a Snake, a new Snake is created (the one Snake inherits from Main_Snake).
As part of the process of creating that Snake object (which, remember inherits from Main_Snake), a new Snake is created.
As part of the process of creating that Snake object (which, remember inherits from Main_Snake), a new Snake is created.
And I think by now you start to see the problem...
I can't really tell you how to fix this, as I have no real idea why you want Snake to be a subclass of Main_Snake. But you can't both have Main_Snake initializing a new Snake, and Snake a subclass of Main_Snake.