Maintaining Invariants Through Object Coupling Mechanisms
Eric Kerfoot, Steve McKeever · 2007
Object invariants are critical components to the specification of object-oriented systems, which define valid states for objects and how they may be interrelated. A complex problem is created when an invariant relies on objects that are externally aliased and modified, since the invariant’s class cannot ensure that modification to these objects preserves the invariant. This paper informally introduces a method of coupling objects called the Colleague Technique, which creates strong relationships between objects whose invariants rely on one another and defines additional conditions to ensure these invariants. The technique builds on the classical technique by providing a method of ensuring object-dependent invariants are maintained by the operations of an object-oriented system. We demonstrate our technique using the Java programming language and the JML specification language. 1.