Centering 3 Buttons with BoxLayout without cutting them off

I ran into 2 other problems. But let me explain one by one.

First I tried to center 3 Buttons with the BoxLayout in the middle of a jframe with the same distance to each button by using Box.createVerticalGlue() and Box.createRigidArea():

    panel.add(Box.createVerticalGlue());
panel.add(Box.createRigidArea(new Dimension(0, 100)));
panel.add(DrawSysButton);
panel.add(Box.createRigidArea(new Dimension(0, 195)));
panel.add(PickBanButton);
panel.add(Box.createRigidArea(new Dimension(0, 195)));
panel.add(ExitButton);
panel.add(Box.createRigidArea(new Dimension(0, 100)));
panel.add(Box.createVerticalGlue());

As soon as I put this into the code, the buttons look like this:

The buttons are cut off on the right side and the distance between Button 1 and 2 seems to be not the same as between Button 2 and Close.

When I remove the Glue and RidigAreas, then the buttons are just in the top center of the frame with many empty space beneath:

I tried a few things to fix that, but nothing helped. Maybe you can help me. I´ll put down here the whole code you need to run this problem by yourself. I tried to create it as minimal as it´s possible.

Thanks in Advance.

import javax.swing.*;
import java.awt.*;
public class main extends JFrame {
//this method loads the first screen that the user sees
public void frameLoader() {
setTitle("3 Centered Buttons");
setResizable(false);
setLocationRelativeTo(null);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS));
//Setting up all buttons and panels we need later on
JPanel panel = new JPanel();
//The Draw-System one
JButton DrawSysButton = new JButton("Button 1");
DrawSysButton.setFocusPainted(false);
DrawSysButton.setPreferredSize(new Dimension(120, 30));
//The Pick&Ban one
JButton PickBanButton = new JButton("Button 2");
PickBanButton.setFocusPainted(false);
PickBanButton.setPreferredSize(new Dimension(120, 30));
//The Exit one
JButton ExitButton = new JButton("Close");
ExitButton.setPreferredSize(new Dimension(120, 30));
//Adding all buttons to the panel
panel.add(Box.createVerticalGlue());
panel.add(Box.createRigidArea(new Dimension(0, 100)));
panel.add(DrawSysButton);
panel.add(Box.createRigidArea(new Dimension(0, 195)));
panel.add(PickBanButton);
panel.add(Box.createRigidArea(new Dimension(0, 195)));
panel.add(ExitButton);
panel.add(Box.createRigidArea(new Dimension(0, 100)));
panel.add(Box.createVerticalGlue());
//set the Frame visible & add the panel to the frame
panel.setAlignmentX(Component.CENTER_ALIGNMENT);
panel.setPreferredSize(new Dimension(120, 500));
panel.setMaximumSize(new Dimension(120, 500));
getContentPane().add(panel);
setSize(400, 500);
setVisible(true);
}
public static void main(String[] args) {
//building the Start-Screen
main StartScreen = new main();
StartScreen.frameLoader();
}
}

Your code has 2 problems leading to this bug:

1. You add your BoxLayout to you contentPane, but add the elements to your panel.
   Replace getContentPane().setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); with panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); so your buttons get added into the layout.

2. You use setSize() and setPreferredSize() instead of letting the layout manage the sizes which should be avoided as explained here. Replace setSize(400, 500); with pack(); and omit all your calls to setPreferredSize(). You should also consider to find a different solution for your rigid areas, for me for example the frame exceeds my screen size due to the large spaces.

With these changes the buttons get displayed properly for me. However they lose some properties. To get them back to all having the same size take a look at https://stackoverflow.com/questions/11536089/making-all-button-size-same, to get them centered take a look at the tutorial.

Also note extending JFrame is discouraged as discussed here