Описание тега boxlayout
BoxLayout is a Java Swing layout manager that allows multiple components to be laid out either vertically or horizontally.
BoxLayout is a layout manager that allows multiple components to be laid out either vertically or horizontally. The components will not wrap so, for example, a vertical arrangement of components will stay vertically arranged when the frame is resized.
Nesting multiple panels with different combinations of horizontal and vertical gives an effect similar to GridBagLayout, without the complexity. The diagram shows two panels arranged horizontally, each of which contains 3 components arranged vertically.
For examples and more details refer to How to Use BoxLayout tutorial.