Primes

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.canvas.*;
import javafx.scene.paint.Color;
import javafx.animation.AnimationTimer;
import javafx.scene.input.KeyCode;

import java.util.*;

public class Primes extends Application{
    private static final int WIDTH = 800;
    private static final int HEIGHT = 600;
    private static final int FPS = 40;

    private int squareSize = 5;
    private int cameraX, cameraY;
    private HashMap<KeyCode, Boolean> keys = new HashMap<>();

    private int frames, fps;

    @Override
    public void start(Stage stage){
        StackPane pane = new StackPane();
        Canvas canvas = new Canvas(WIDTH, HEIGHT);
        pane.getChildren().add(canvas);
        GraphicsContext gc = canvas.getGraphicsContext2D();

        canvas.setOnScroll(e -> {
            if (e.getDeltaY() > 0){
                this.squareSize += 1;
            } else if (e.getDeltaY() < 0){
                this.squareSize -= 1;
            }

            this.squareSize = Math.min(150, Math.max(this.squareSize, 1));
        });

        canvas.setFocusTraversable(true);
        canvas.setOnKeyPressed(e -> this.keys.put(e.getCode(), true));
        canvas.setOnKeyReleased(e -> this.keys.put(e.getCode(), false));

        AnimationTimer timer = new AnimationTimer(){
            @Override
            public void handle(long time){
                update(gc);
                Primes.this.frames++;
                stage.setTitle("Prime numbers - FPS:"+Primes.this.fps); // Set FPS title
            }
        };
        timer.start();

        Thread fpsCounter = new Thread(() -> {
            while (true){
                try {
                    this.fps = this.frames;
                    this.frames = 0;
                    Thread.sleep(1000);
                } catch (InterruptedException ex){
                    ex.printStackTrace();
                }
            }
        });
        fpsCounter.setDaemon(true);
        fpsCounter.start();

        Scene scene = new Scene(pane, WIDTH, HEIGHT);
        stage.setScene(scene);
        stage.setResizable(false);
        stage.show();
    }

    private void update(GraphicsContext gc){
        gc.clearRect(0, 0, WIDTH, HEIGHT);
        gc.setFill(Color.BLACK);
        gc.fillRect(0, 0, WIDTH, HEIGHT);

        final int cameraSpeed = 4;
        if (this.keys.getOrDefault(KeyCode.W, false)){
            this.cameraY -= cameraSpeed;
            this.keys.put(KeyCode.W, false);
        } else if (this.keys.getOrDefault(KeyCode.A, false)){
            this.cameraX -= cameraSpeed;
            this.keys.put(KeyCode.A, false);
        } else if (this.keys.getOrDefault(KeyCode.S, false)){
            this.cameraY += cameraSpeed;
            this.keys.put(KeyCode.S, false);
        } else if (this.keys.getOrDefault(KeyCode.D, false)){
            this.cameraX += cameraSpeed;
            this.keys.put(KeyCode.D, false);
        } else if (this.keys.getOrDefault(KeyCode.ESCAPE, false)){
            System.exit(0);
        }

        for (int i = 0; i < WIDTH; i += squareSize){
            for (int j = 0; j < HEIGHT; j += squareSize){
                int xpos = i/squareSize+this.cameraX;
                int ypos = j/squareSize+this.cameraY;
                if (xpos < 0 || ypos < 0) continue;
                int id = xpos ^ ypos; //xpos+ypos*WIDTH;
                if (isPrime(id)){
                    for (int x = 0; x < squareSize; x++){
                        for (int y = 0; y < squareSize; y++){
                            gc.getPixelWriter().setColor(i+x, j+y, getColor(id));
                        }
                    }
                }
            }
        }
    }

    private static Color getColor(int prime){
        Random random = new Random(prime);
        return Color.color(random.nextDouble(), random.nextDouble(), random.nextDouble());
    }

    private static boolean isPrime(int num){
        for (int i = 2; i <= Math.sqrt(num); i++){
            if (num % i == 0){
                return false;
            }
        }

        return true;
    }

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