why is velocity not decreasing in 2d movement simulation?

I am trying to make a program where object1 movement is warped by the gravity of object2. It should get flung. However, for some reason the velocity never decreases or goes negative. I expect for the velocity to change in both directions, but this does not happen. Can anyone tell me why? Here is the code.

Sim.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Sim extends JPanel {

    private static final long serialVersionUID = -2669101810074157675L;
    public static final int PREF_W = 800, PREF_H = 600;

    private Mass object1, object2;

    private Sim() {
        this.setFocusable(true);
        this.setBackground(Color.WHITE);

        double[] vect1 = {1, 0}, vect2 = {0, 0};
        object1 = new Mass(new Point(PREF_W / 2 - 100, PREF_H / 2 - 100), vect1, 10);
        object2 = new Mass(new Point(PREF_W / 2 + 100, PREF_H / 2 + 100), vect2, 30);
        object2.lock();

        gameTimer.start();

    }

    private Timer gameTimer = new Timer(1000 / 30, new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {

            double[] v = Mass.vector(object1, object2);
            object1.dx += v[0];
            object1.dy += v[1];

            Point p = new Point(
                    (int) (object1.center.x + object1.dx),
                    (int) (object1.center.y + object1.dy)
            );
            object1.center = p;

            System.out.println("[" + object1.center.x + "," + object1.dy + "]");
        }
    });

    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        g2.fillOval(
                (int) object1.center.x - (int) object1.radius,
                (int) object1.center.y - (int) object1.radius,
                (int) object1.radius,
                (int) object1.radius
        );

        g2.fillOval(
                (int) object2.center.x - (int) object2.radius,
                (int) object2.center.y - (int) object2.radius,
                (int) object2.radius,
                (int) object2.radius
        );

        g2.drawLine(object1.center.x, object1.center.y, object2.center.x, object2.center.y);


        repaint();

    }

    /* METHODS FOR CREATING JFRAME AND JPANEL */

    public Dimension getPreferredSize() {
        return new Dimension(PREF_W, PREF_H);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("Gravity Simulation");
                JPanel gamePanel = new Sim();

                frame.getContentPane().add(gamePanel);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
            }
        });
    }

}

Mass.java

import java.awt.Point;

public class Mass {

    public static double G = 1f;
    public static double deltaTime = 1;

    public Point center;
    public double mass;
    public double radius;

    public double dx = 0;
    public double dy = 0;

    public boolean locked = false;

    public Mass(Point center, double[] vect, double mass) {
        this.center = center;
        this.dx = vect[0];
        this.dy = vect[1];
        this.mass = mass;
        this.radius = mass;
    }

    public void lock() {
        this.locked = true;
    }

    public void unlock() {
        this.locked = false;
    }

    public static double distance(Mass obj1, Mass obj2) {

        double dX = obj1.center.x - obj2.center.x;
        double dY = obj1.center.y - obj2.center.y;

        double ans = Math.sqrt(Math.pow(dX, 2) + Math.pow(dY, 2));
        return (double) ans;

    }

    public static double force(Mass obj1, Mass obj2) {

        double ans = ((obj1.mass * obj2.mass) / Math.pow(distance(obj1, obj2), 2)) * G;
        return (double) ans;

    }

    public static double[] vector(Mass obj1, Mass obj2) {
        double force = force(obj1, obj2);

        double dX = Math.abs(obj1.center.x - obj2.center.x);
        double dY = Math.abs(obj1.center.y - obj2.center.y);

        double udX = dX / distance(obj1, obj2);
        double udY = dY / distance(obj1, obj2);

        double fx = -(udX * force);
        double fy = -(udY * force);

        double x = obj1.dx + fx / obj1.mass * deltaTime;
        double y = obj1.dy + fy / obj1.mass * deltaTime;

        double[] v = {x, y};
        return v;

    }

}

Thank you in advance. I derived my formula from F = G(m1*m2)/r^2.