How to center buttons in my java game menu

So, basically, I've never really worked with windows in java, and I need help centering things. I tried a bunch of things, but no matter what, I can't center my buttons on my java menu.

Here's my main class:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.image.BufferedImage;
import java.awt.image.ImageObserver;
import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
import java.awt.Image;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
public class window extends JPanel {
private static final long serialVersionUID = 1L;
private BufferedImage canvas;
public window(int width, int height) {
canvas = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
}
public Dimension getPreferredSize() {
return new Dimension(canvas.getWidth(), canvas.getHeight());
}
public void paint(Graphics g){ 
//		    double CanvasTileHeight = (canvas.getHeight()/16)+1;
//		    double CanvasTileWidth = (canvas.getWidth()/16)+1;
//		    
//		    OpenSimplexNoise noise = new OpenSimplexNoise();
//		    
//		    for(int j=0;j<CanvasTileWidth;j++) {
//		    	double NoiseForCurrentLoopPos;
//		    	if (((noise.eval(j,2)+1)*2)+16 < CanvasTileHeight) {
//		    		NoiseForCurrentLoopPos = ((noise.eval(j,2)+1)*2)+16;
//		    	} else {
//		    		NoiseForCurrentLoopPos = CanvasTileHeight;
//		    	}
//		    	for(int i=(int) CanvasTileHeight;i>NoiseForCurrentLoopPos;i--) {
//		    			Image sand = Toolkit.getDefaultToolkit().getImage("src/images/misc/sand.png");
//		    			g.drawImage(sand, j*16, i*16, this);		    		
//		    	}
//		    }
//		    
//		    Image image = Toolkit.getDefaultToolkit().getImage("src/images/misc/Player_Placeholder1.png");
//		    
//		 ImageObserver paintingChild = null;
//		 g.drawImage(image, canvas.getWidth()/2-image.getWidth(paintingChild)/2, canvas.getHeight()/2-image.getHeight(paintingChild)/2, this);
//		    
}
public static void main(String[] args) throws ClassNotFoundException, IOException {
int width = 640;
int height = 480;
JFrame frame = new JFrame("Example Frame");
window panel = new window(width, height);
frame.add(panel);
frame.pack();
frame.setVisible(true);
frame.setResizable(false);
JPanel buttons = new JPanel();
BoxLayout boxlayout = new BoxLayout(buttons, BoxLayout.Y_AXIS);
buttons.setLayout(boxlayout);
buttons.setBorder(new EmptyBorder(new Insets(150, 200, 150, 200)));
JLabel bottomLabel = new JLabel("GAME NAME HERE", SwingConstants.CENTER);
buttons.add(bottomLabel);
JButton jb1 = new JButton("Button 1");
JButton jb2 = new JButton("Button 2");
JButton jb3 = new JButton("Button 3");
jb1.setAlignmentX(SwingConstants.CENTER);
jb2.setAlignmentX(SwingConstants.CENTER);
jb3.setAlignmentX(SwingConstants.CENTER);
buttons.add(Box.createRigidArea(new Dimension(0, 10)));
buttons.add(jb1); 
buttons.add(Box.createRigidArea(new Dimension(0, 10)));
buttons.add(jb2);
buttons.add(Box.createRigidArea(new Dimension(0, 10)));
buttons.add(jb3);
frame.add(buttons);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//        loadtest();
//        System.out.println(Arrays.toString(((String) test1).split(",")));
//        
//        savetest();
dirtest();
}
public static void savetest() {
String TestArray[] = {"hi87er629087029648276540982", "hi2", "hi3", "hi4", "Not gonna keep going on like this lol"};
String Test = TestArray[0];
String world = "testworld101022";
for (int k = 0; k < TestArray.length-1; k++) {
Test = Test + "," + TestArray[k+1];
}
new File("src\\saves\\" + world).mkdir();
try(FileOutputStream f = new FileOutputStream("src\\saves\\" + world + "\\chunk1savetest1.txt");
ObjectOutput s = new ObjectOutputStream(f)) {
s.writeObject(Test);
} catch (FileNotFoundException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
}
static Object test1 = null;
public static void loadtest() {
String world = "testworld101022";
try(FileInputStream in = new FileInputStream("src\\saves\\" + world + "\\chunk1savetest1.txt");
ObjectInputStream s = new ObjectInputStream(in)) {
test1 = s.readObject();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} 
}
public static void dirtest() {
File dir = new File("src\\saves");
File[] files = dir.listFiles();
FileFilter fileFilter = new FileFilter() {
public boolean accept(File file) {
return file.isDirectory();
}
};
files = dir.listFiles(fileFilter);
System.out.println(files.length);
if (files.length == 0) {
System.out.println("No saves yet!");
} else {
for (int i = 0; i< files.length; i++) {
File filename = files[i];
System.out.println(filename.toString());
}
}
}
}

My problem is when I run it, this is what happens:

So, the buttons and/or test are not centered. I don't understand why.

My problem is, the buttons should be about where the red line on the image is, but no matter what I do, I can't get it to work.

I tried centering it with SwingConstants.CENTER, but that diden't work, so I also tried Component.CENTER_ALIGNMENT, but that did the exact same thing. I found that doing multiple different things like changing the code to

jb1.setAlignmentX(Component.CENTER_ALIGNMENT);
jb2.setAlignmentX(SwingConstants.CENTER);
jb3.setAlignmentX(SwingConstants.CENTER);

makes it like this:

so basically it makes it so the 2 that are different from the one I changed are correctly centered, but the one I changed it not. All the images and stuff are probably unnecessary, but I hope I got across what I need help with! thanks =)

You can use BoxLayout to do that, take a look at the following code:

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import java.awt.Dimension;
import java.util.Arrays;
public class Main
{
public static void main(final String[] args)
{
final JLabel label = new JLabel("GAME NAME HERE");
final JButton button1 = new JButton("Button 1");
final JButton button2 = new JButton("Button 2");
final JButton button3 = new JButton("Button 3");
final JPanel centerPanel = createCenterVerticalPanel(5, label, button1, button2, button3);
final JFrame frame = new JFrame();
frame.add(centerPanel);
frame.setVisible(true);
frame.pack();
}
private static JPanel createCenterVerticalPanel(final int spaceBetweenComponents, final JComponent... components)
{
final JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
Arrays.stream(components).forEach(component -> {
component.setAlignmentX(JPanel.CENTER_ALIGNMENT);
panel.add(component);
panel.add(Box.createRigidArea(new Dimension(0, spaceBetweenComponents)));
});
return panel;
}
}

If you also want to center a panel vertically in a frame, just use frame.setLayout(new GridBagLayout()). Cheers!