Okno

import javax.swing.JFrame;

import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeListener;
import java.text.*;

public class Okno extends JFrame {

    JFormattedTextField aField, vField;
    JLabel aLabel, vLabel, degLabel, msLabel;
    JTextArea textArea;
    Wykres wykres;
    JPanel panel, buttonPanel;
    JButton okButton;
    
    public Okno() {
        super();
        prepareWindow();
    }
    
    void prepareWindow() {
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        setTitle("Rzut ukosny");

        panel = new JPanel();
        panel.setLayout(new BorderLayout());

        // TextFields, Buttons and labels
        aField = new JFormattedTextField();
        aField.setColumns(6);
        aField.setText("35.0");
        aLabel = new JLabel("Kat a: ", JLabel.CENTER);
        aLabel.setFont(aLabel.getFont().deriveFont(Font.BOLD, 14f));
        degLabel = new JLabel("\u00b0", JLabel.CENTER);
        vField = new JFormattedTextField();
        vField.setColumns(6);
        vField.setText("100");
        vLabel = new JLabel("Predkosc v: ", JLabel.CENTER);
        vLabel.setFont(aLabel.getFont().deriveFont(Font.BOLD, 14f));
        msLabel = new JLabel("m/s", JLabel.CENTER);
        ImageIcon okButtonIcon = createImageIcon("ok.png", "ok icon");
        okButton = new JButton("OK", okButtonIcon);
        
        okButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                double a = Double.parseDouble(aField.getText());
                double v = Double.parseDouble(vField.getText());
                newSimulation(a, v);
            }
        });

        // Panel stuff
        buttonPanel = new JPanel();
        buttonPanel.add(aLabel);
        buttonPanel.add(aField);
        buttonPanel.add(degLabel);
        buttonPanel.add(vLabel);
        buttonPanel.add(vField);
        buttonPanel.add(msLabel);
        buttonPanel.add(okButton);
        panel.add(buttonPanel, "North");

        wykres = new Wykres();
        panel.add(wykres, "Center");

        textArea = new JTextArea(10, 60);
        textArea.setEditable(false);
        panel.add(new JScrollPane(textArea), "South");

        setContentPane(panel);
    }


    protected ImageIcon createImageIcon(String path, String description) {
        java.net.URL imgURL = getClass().getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL, description);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
        
    }
    
    void newSimulation(double kat, double predkoscPoczatkowa) {
        try {
            textArea.setText("");
            RzutUkosny obliczenia = new RzutUkosny(kat, predkoscPoczatkowa);
            wykres.setObliczenia(obliczenia);

            NumberFormat nf = NumberFormat.getInstance();
            nf.setMaximumFractionDigits(3);
            
            textArea.setText("# Rzut Ukosny:\n\n");
            textArea.append("Kat: " + nf.format(obliczenia.angle) + "[rad]\n");
            textArea.append("Predkosc: " + nf.format(obliczenia.vel) + "[m/s]\n");
            textArea.append("Predkosc pozioma: " + nf.format(obliczenia.velX) + "[m/s]\n");
            textArea.append("Predkosc pionowa: " + nf.format(obliczenia.velY) + "[m/s]\n");
            textArea.append("Wysokosc maksymalna: " + nf.format(obliczenia.hMax) + "[m]\n");
            textArea.append("Czas wznoszenia: " + nf.format(obliczenia.tWznoszenia) + "[s]\n");
            textArea.append("Czas calkowity: " + nf.format(obliczenia.tCalkowity) + "[s]\n");

            wykres.newSimulation(obliczenia);
        } catch (Exception e) {
            textArea.setText("Wystapil blad!");
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        Okno o = new Okno();
        o.pack();
        o.setLocationRelativeTo(null);
        o.setVisible(true);
    }
}

RzutUkosny

public class RzutUkosny {

    final double g = 9.80665;

    final public double angle;
    final public double vel;

    final public double velX, velY;
    final public double hMax;
    final public double tWznoszenia;
    final public double tCalkowity;

    public RzutUkosny(double katRzutu, double predkoscPoczatkowa) {

        double tmp = Math.toRadians(katRzutu);
        if (tmp < 0) {
            tmp = 0;
        } else if (tmp > 90) {
            tmp = 90;
        }

        vel = predkoscPoczatkowa;
        angle = tmp;

        velX = vel * Math.cos(angle);
        velY = vel * Math.sin(angle);
        hMax = (velY * velY) / (2*g);
        tWznoszenia = velY / g;
        tCalkowity = 2 * tWznoszenia;
    }

    // zwraca wartosc y dla danego x
    public double getYForX(double x) {
        return x * Math.tan(angle) 
                - ( g / (2 * velX * velX) ) * x * x;
    }

    // zwraca wartosc x w chwili czasu t
    public double getXForT(double t) {
        return velX * t;
    }

    // zwraca wartosc y w chwili czasu t
    public double getYForT(double t) {
        return velY * t - (g/2) * t * t;
    }
}

Wykres

import javax.swing.JPanel;

import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import java.util.Timer;
import java.text.*;

public class Wykres extends JPanel {
    final int marginX = 50;
    final int marginY = 50;

    int screenWidth = 800;
    int screenHeight = 600;

    double currentTime = 0;
    double timeStep = 0.05;
    double imageScale = 1;

    RzutUkosny obliczenia = null;

    public void setObliczenia(RzutUkosny obliczenia) {
        this.obliczenia = obliczenia;
    }

    BufferedImage image = null;

    public Wykres() {
        image = newImage(screenWidth, screenHeight);
        drawAxesAndLegend(image);
        setPreferredSize(new Dimension(screenWidth, screenHeight));
    }

    public void paintComponent(Graphics g) {
        g.drawImage(image, 0, 0, null);
    }

    BufferedImage newImage(int w, int h) {
        BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        img.createGraphics();
        return img;
    }

    void drawAxesAndLegend(BufferedImage img) {
        Graphics2D g = (Graphics2D) img.getGraphics();

        g.setColor(Color.LIGHT_GRAY);
        g.fillRect(0, 0, img.getWidth(), img.getHeight());

        g.setColor(Color.black);
        g.drawLine(marginX, screenHeight - marginY, screenWidth - marginX, screenHeight - marginY);
        g.drawLine(marginX, marginY, marginX, screenHeight - marginY);

        g.drawLine(marginX - 10, marginY, marginX + 10, marginY);
        g.drawLine(screenWidth - marginX, screenHeight - marginY - 10, screenWidth - marginX, screenHeight - marginY + 10);

        NumberFormat nf = NumberFormat.getInstance();
        nf.setMaximumFractionDigits(2);

        g.drawString(nf.format(imageScale * (screenHeight - 2 * marginY)) + " [m]", marginX, marginY - 10);
        g.drawString(nf.format(imageScale * (screenWidth - 2 * marginX)) + " [m]", screenWidth - 2 * marginX, screenHeight - marginY / 2);

        g.dispose();
    }

    public void newSimulation(RzutUkosny obliczenia) {
        this.obliczenia = obliczenia;
        scaleImage();
        image = newImage(screenWidth, screenHeight);
        drawAxesAndLegend(image);
        currentTime = 0;
        repaint();

        draw();
    }
    
    public void draw() {
        Graphics2D g = (Graphics2D) image.getGraphics();
        g.setColor(Color.BLUE);
        for (double screenX = 0; screenX <= screenWidth - (marginX * 2); screenX += 1.0) {
            System.out.println("x:  " + screenX + "y: " + obliczenia.getYForX(screenX));
            g.drawRect((int)screenX + marginX, - (int) obliczenia.getYForX(screenX) + (screenHeight - marginY), 3, 3);
        }
        g.dispose();
    }

    void scaleImage() {
        imageScale = 1 * (obliczenia.hMax / screenWidth - 100);
    }
}