In single-threaded environments, the use of `+this+` in constructors is normal, and expected. But in multi-threaded environments, it could expose partially-constructed objects to other threads, and should be used with caution.
The classic example is a class with a `+static+` list of its instances. If the constructor stores `+this+` in the list, another thread could access the object before it's fully-formed. Even when the storage of `+this+` is the last instruction in the constructor, there's still a danger if the class is not `+final+`. In that case, the initialization of subclasses won't be complete before `+this+` is exposed.
This rule raises an issue when `+this+` is assigned to any globally-visible object in a constructor, and when it is passed to the method of another object in a constructor
