Your current code looks nothing like the description you give of what you want. It sounds like you need
- a top-level vertical box
- a horizontal box
- button
- gap
- button
- gap
- button
- a horizontal box
So something like
Box vbox = Box.createVerticalBox();
Box hbox = Box.createHorizontalBox();
hbox.add(new JButton("Button"));
hbox.add(Box.createHorizontalStrut(10));
hbox.add(new JButton("Hello"));
vbox.add(hbox);
vbox.add(Box.createVerticalStrut(100));
vbox.add(new JButton("Button2"));