What is a client property?
Swings base class for all components,
provides following methods that allows you to set and get user-defined
public final Object getClientProperty(Object key);
public final void putClientProperty(Object key, Object value);
Some Swing components use client properties to change their
behavior. E.g. for JLabel you can disable HTML display with
Boolean.TRUE); You can use client properties to store any
information in components. Visit Finally...
Client Properties You Can Use on Ben Galbraith's Blog for a use
Define client properties
Edit client properties
If you've defined client properties, JFormDesigner shows them in the Properties view, where you can set the values of the client properties.