Java's GridBagLayout layout manager allows the users to specify constraints that constrain the sizes and positions of components to be laid out in a grid board. However, the constraints are very limited. Constraints are all directional, and it is impossible to describe arbitrary layout of components. The designers of Java left a heavy burden to the programmers in exchange for a easy-to-implement and fast layout algorithm. Constraints in DJ are much more powerful. For example, it would take an order of magnitude more Java code to specify the keyboard in our Calculator example.