import javafx.application.Application;
    import javafx.stage.Stage;
    import java.util.Random;
    import javafx.geometry.Pos;
    import java.awt.*;

    public class App extends Application {
     public void paint(Graphics page) {
    Random generator = new Random();

    int random, randomx, randomy;
    int x, y;
    int width, height;


    random = generator.nextInt(75) + 25;
    randomx = generator.nextInt(400);
    randomy = generator.nextInt(300);
    page.setColor(Color.black);
    x = randomx;
    y = randomy;
    width = random * 2;
    height = random * 2;
    page.drawOval(x, y, width, height);
}

    @Override
public void start(Stage primaryStage) {

}
    }