Jessica Kerr "Functional Principles for Object Oriented Development"

How is an expert OO developer to improve on his craft? By learning from other paradigms! These six principles of the functional style can apply to OO. Some of these principles are part of good practice already; some express patterns both old and new; all give us different ways of thinking about problems. For developers without expertise in functional programming, examples in Java provide new techniques for writing clear, quality code.