How can I scroll more than one object at the same time?

“How can I make my Game.class scroll more than one instance of Pipes.class while adding a preset distance between them? “

Here’s some simple logic. You want to use a data structure to hold you pipes. What this data structure will hold is whatever data is required to paint then, like x, y, coordinates. For this task, I prefer just to create a new class with it’s own draw method, that I pass the paintComponent‘s Graphics context to. For example

public class Pipe {
    int x;
    int y;
    public class Pipe(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public void drawPipe(Graphics g) {
        g.fillRect(x, y, 50, 100);
    }
}

Now this is just an example class. The above only draws a rectangle, but this is just to show you what you should be doing.

So next you want to have the data structure to hold three Pipe objects, like an array. I prefer to use a List. You’ll want that List in your Pipes class, and add three Pipe object to it. You can specify the x to be anything you like, to keep them the same distance apart

public class Pipes extends JPanel {
    List<Pipe> pipes = new ArrayList<Pipe>();

    public Pipes() {
        pipes.add(new Pipe(50, 100));
        pipes.add(new Pipe(150, 100));
        pipes.add(new Pipe(250, 100));
    }
}

Now in the paintComponent method, all you need to do is loop through them and use its drawPipe method

protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    for ( Pipe pipe : pipes ){
        pipe.drawPipe(g);
    }
}

Now you move them all you need to do is move there x positions in the timer, and call repaint. You may also want to check against the x to make sure it doesn’t do off the screen, or if you moving them the right, you could put them the the very left then whey go off the screen, like a conveyor belt. So you could do something like this

private static final int X_INC = 5;
...
Timer timer = new Timer(40, new ActionListener(){
    public void actionPerformed(ActionEvent e) {
        for (Pipe pipe : pipes ){
            if (pipe.x >= screenWidth) {
                pipe.x = 0;
            } else {
                pipe.x += X_INC;
            }
        }
        repaint();
    }
});

As you can see, what I do is loop through the List and just change all their x coordinates, then repaint(). So you can create your own Pipe class with whatever values you need to paint, and just move them around in the loop.

---

For the changing of speed, instead of using a hard coded vakue like 10 for the timer, use a variable delay, that you can change like with the click of a button

int delay = 100;
JButton speedUp = new JButton("Speed UP");
JButton slowDown = new JButton("Slow Down");
Timer timer = null;
public Pipes() {
    timer = new Timer(delay, new ActionListener(){
        ...
    });
    timer.start();

    speedUp.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            if (!((delay - 20) < 0)) {
                delay -=20;
                timer.setDelay(delay);
            }
        }
    });
    // do the same for slowDown, but decrease the delay
}

---

Test this out

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;


public class Mario extends JPanel {

    private static final int D_W = 800;
    private static final int D_H = 300;
    private static final int X_INC = 5;

    BufferedImage bg;
    BufferedImage pipeImg;

    List<Pipe> pipes = new ArrayList<>();

    int delay = 50;

    Timer timer = null;

    public Mario() {

        try {
            bg = ImageIO.read(new URL("http://farm8.staticflickr.com/7341/12338164043_0f68c73fe4_o.png"));
            pipeImg = ImageIO.read(new URL("http://farm3.staticflickr.com/2882/12338452484_7c72da0929_o.png"));
        } catch (IOException ex) {
            Logger.getLogger(Mario.class.getName()).log(Level.SEVERE, null, ex);
        }

        pipes.add(new Pipe(100, 150, pipeImg));
        pipes.add(new Pipe(400, 150, pipeImg));
        pipes.add(new Pipe(700, 150, pipeImg));

        timer = new Timer(delay, new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                for (Pipe pipe : pipes) {
                    if (pipe.x > D_W) {
                        pipe.x = 0;
                    } else {
                        pipe.x += X_INC;
                    }
                }
                repaint();
            }
        });
        timer.start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(bg, 0, 0, getWidth(), getHeight(), this);
        for (Pipe pipe : pipes) {
            pipe.drawPipe(g);
        }
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(D_W, D_H);
    }

    public class Pipe {

        int x;
        int y;
        Image pipe;

        public Pipe(int x, int y, Image pipe) {
            this.x = x;
            this.y = y;
            this.pipe = pipe;
        }

        public void drawPipe(Graphics g) {
            g.drawImage(pipe, x, y, 75, 150, Mario.this);
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("Mario Pipes");
                frame.add(new Mario());
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}