Java FX Exception beim start

[Lucaaa]

Wenn ich mein Programm starte passiert folgendes:

Anzahl an Unterrichtsstunden:
3
Anzahl an Unterrichtsstunden:
Exception in Application constructor
Exception in thread "main" java.lang.RuntimeException: Unable to construct Application instance: class MainWindow
 at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:907)
 at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
 at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
 at java.lang.reflect.Constructor.newInstance(Unknown Source)
 at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$160(LauncherImpl.java:819)
 at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
 at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
 at java.security.AccessController.doPrivileged(Native Method)
 at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
 at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
 at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
 at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
 ... 1 more
Caused by: java.util.NoSuchElementException
 at java.util.Scanner.throwFor(Unknown Source)
 at java.util.Scanner.next(Unknown Source)
 at java.util.Scanner.nextInt(Unknown Source)
 at java.util.Scanner.nextInt(Unknown Source)
 at MainWindow.<init>(MainWindow.java:17)
 ... 13 more

Hier der Code:

import java.util.Scanner;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
public class MainWindow extends Application {
 int numberHouers = 8;
 
 
 
  public MainWindow() {
   System.out.println("Anzahl an Unterrichtsstunden:");
   Scanner scanner = new Scanner(System.in);
   numberHouers = scanner.nextInt();
   scanner.close();
   launch();
 }
 
 
 @Override
 public void start(Stage s) throws Exception {
  //Parent layout = FXMLLoader.load(new File("res/layout/test.xml").toURI().toURL());
  GridPane layout = new GridPane();
  layout.gridLinesVisibleProperty().set(true);
  
  
  Label[] days = new Label[8];
  String[] dayNames = new String[] {"Stunde","Montag","Dienstag","Mittwoch","Donnerstag","Freitag","Samstag","Sonntag"};
  for(int i = 0; i<days.length; i++) {
   days[i] = new Label(dayNames[i]);
   days[i].setStyle("-fx-background-color: #aaaaff; -fx-border-color:green; -fx-padding: 10; ");
   days[i].setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
   GridPane.setFillWidth(days[i], true);
   GridPane.setFillHeight(days[i], true);
   layout.add(days[i], i, 0);
  }
  
  
  Label[] houers = new Label[numberHouers];
  for(int i = 0; i<houers.length; i++) {
   houers[i] = new Label(i+1+". Stunde");
   houers[i].setStyle("-fx-background-color: #aaaaff; -fx-border-color:green; -fx-padding: 10; ");
   houers[i].setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
   GridPane.setFillWidth(houers[i], true);
   GridPane.setFillHeight(houers[i], true);
   layout.add(houers[i], 0, i+1);
  }
  
  
  
  Scene scene = new Scene((layout));
  
  
  
  s.setScene(scene);
  s.show();
 }
}

public class Main  {
 
 
 public static void main(String[] args) {
  new MainWindow();
 }
 
 
 
 
 
}

Ich hoffe, mir kann wer helfen

 

[httpdigest]

Das Problem ist, dass du:
1. den Konstruktor von MainWindow selber in Main aufrufst
2. innerhalb des Konstruktors den System.in Stream schließst (per Scanner.close(), der wiederum den darunterliegenden Stream schließt)
3. innerhalb des Konstruktors die _statische_ launch() Methode der JavaFX Application Klasse aufrufst
4. diese statische launch Methode ihrerseits die Klasse MainWindow erneut instanziiert
5. und dann der Scanner natürlich nichts mehr liefert, weil System.in bereits geschlossen ist

Lösung: Instanziiere die MainWindow Klasse nichts selbst, sondern rufe Application.launch(MainWindow.class) innerhalb der main() Methode auf und nicht innerhalb des Konstruktors von MainWindow.

 

[Lucaaa]

ok danke. habs schon selbst geschafft

public static void main(String[] args) {
  Application.launch(MainWindow.class, args);
 }

Wie du ja sagtest.