FlowLayout performs "pressure" from the right, so as all components are trying to take their minimal widths. Contrary, BoxLayout tries to spread all components to fill entire height of the space.
Can I add some filler as last component or something to make all components have minimal heights in BoxLayout?
You could use Box.createGlue(), which returns a component that takes up as much space as the BoxLayout will give it. Adding it to the bottom of a vertical BoxLayout will scrunch the other components to the top.
You could also use nested layouts.
来源：https://stackoverflow.com/questions/12651043/how-to-make-boxlayout-behave-as-vertical-flowlayout