Import the adjacency matrix of the digraph and output the graph with JavaFX and a graphic user interface. Draw the arrows of the digraph based on the line object of JavaFX. Show me the code by using java language.

Sure, here is an example code that imports the adjacency matrix of a digraph, outputs the graph with JavaFX, and draws the arrows of the digraph based on the line object:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class DigraphGUI extends Application {
    
    // Define the adjacency matrix of the digraph
    int[][] adjMatrix = {
        {0, 1, 0, 0},
        {1, 0, 1, 1},
        {0, 0, 0, 1},
        {0, 0, 1, 0}
    };

    // Define the positions of the nodes
    int[] nodeX = {50, 150, 250, 350};
    int[] nodeY = {50, 150, 150, 250};

    @Override
    public void start(Stage primaryStage) {
        // Create a canvas to draw the graph on
        Canvas canvas = new Canvas(400, 300);
        GraphicsContext gc = canvas.getGraphicsContext2D();

        // Draw the nodes
        for (int i = 0; i < adjMatrix.length; i++) {
            gc.setFill(Color.BLUEVIOLET);
            gc.fillOval(nodeX[i] - 10, nodeY[i] - 10, 20, 20);
            gc.setFill(Color.WHITE);
            gc.fillText(Integer.toString(i), nodeX[i] - 3, nodeY[i] + 3);
        }

        // Draw the edges and arrows
        for (int i = 0; i < adjMatrix.length; i++) {
            for (int j = 0; j < adjMatrix.length; j++) {
                if (adjMatrix[i][j] == 1) {
                    gc.setStroke(Color.BLACK);
                    gc.setLineWidth(1.5);
                    gc.strokeLine(nodeX[i], nodeY[i], nodeX[j], nodeY[j]);

                    double angle = Math.atan2(nodeY[j] - nodeY[i], nodeX[j] - nodeX[i]);
                    double arrowX = Math.cos(angle - Math.toRadians(20)) * 10 + nodeX[j];
                    double arrowY = Math.sin(angle - Math.toRadians(20)) * 10 + nodeY[j];
                    gc.strokeLine(nodeX[j], nodeY[j], arrowX, arrowY);

                    arrowX = Math.cos(angle + Math.toRadians(20)) * 10 + nodeX[j];
                    arrowY = Math.sin(angle + Math.toRadians(20)) * 10 + nodeY[j];
                    gc.strokeLine(nodeX[j], nodeY[j], arrowX, arrowY);
                }
            }
        }

        // Create a scene and add the canvas to it
        StackPane root = new StackPane();
        root.getChildren().add(canvas);
        Scene scene = new Scene(root, 400, 300);

        // Set the stage and show the scene
        primaryStage.setTitle("Digraph GUI");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

In this code, we first define the adjacency matrix of the digraph and the positions of the nodes. Then, we create a canvas and draw the nodes on it. Next, we iterate through the adjacency matrix and draw the edges and arrows based on the line object of JavaFX. Finally, we create a scene and add the canvas to it, then show the scene on the stage.