gap parameter

The basic example.
FormLayout formLayout = new FormLayout(8, 5, 8, 8);

No external gaps, and default internal gaps of 5.
FormLayout formLayout = new FormLayout();

Internal vertical gaps only.
FormLayout formLayout = new FormLayout(8, 0, 0, 0);

Internal horizontal gaps only.
FormLayout formLayout = new FormLayout(0, 5, 0, 0);

External vertical gaps only.
FormLayout formLayout = new FormLayout(0, 0, 8, 0);

External horizontal gaps only.
FormLayout formLayout = new FormLayout(0, 0, 0, 8);