StackOverflowError (java fx)

Question

I am writing a code with a class for drawing a line and another class to display the line. The point of the class is for me to easily write multiple lines and make my code a bit more organized. But for some reason, I am getting a StackOverflow error whenever I run it. I am unsure on why this is happening. it also gives me a RunTimeException and a lot of different error messages like "Exception in application start method". I am unsure on what those are supposed to mean.

This is the error messages it gives me:

    Exception in Application start method
    java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:873)
    Caused by: java.lang.RuntimeException: Exception in Application start method
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$1(LauncherImpl.java:182)
        at java.lang.Thread.run(Thread.java:748)
    Caused by: java.lang.StackOverflowError
    at Line.<init>(Main.java:133)
    at Line.<init>(Main.java:133)
    at Line.<init>(Main.java:133) //this just repeats a bunch of times
Exception running application Main

This is the code:

import javafx.scene.shape.Ellipse;
import javafx.scene.Node;
import javafx.scene.paint.Paint;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.scene.shape.Ellipse;
import javafx.scene.shape.Rectangle;

class Line{

    public Line line;

    public Line(int x1,  int y1, int x2, int y2){

        Line line = new Line(x1, y1, x2, y2);
    }

    public void setFill(Paint p) {
        line.setFill(p);
    }

}

public class Main extends Application {
    private Pane root;
    @Override
    public void start(Stage primaryStage) {
        root = new Pane();

        Line line1 = new Line(250,250,450,450);

        root.getChildren().addAll((Collection<? extends Node>) line1);
        line1.setFill(Color.BLACK);

        Scene scene = new Scene(root, 500, 500);
        primaryStage.setTitle("Empty");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {

        Application.launch(args);
    }


}

Answer 1

That is because this never ends.

public Line(int x1,  int y1, int x2, int y2){

        Line line = new Line(x1, y1, x2, y2);
    }

While creating a new object, you are calling the constructor. And within it, it's creating an object, which leads to calling constructor again and so on.
So do this instead:

class Line{

    int x1,x2,y1,y2;

    public Line(int x1,  int y1, int x2, int y2){

        this.x1 = x1;
        this.x2 = x2;
        this.y1 = y1;
        this.y2 = y2;
    }

}

You don't need to create setFill() function as it's imported. Simply use the function.