It's all private code, so I can't give you a citation, but I've often helped junior devs with bugs due to this. The most common way to get there starts with cr

It's all private code, so I can't give you a citation, but I've often helped junior devs with bugs due to this. The most common way to get there starts with creating a "bean" object. And then, since it's a bean, it has mutable getters and setters. On everything, because that's just the standard way that people are (or at least were) taught to do these things in Java. And then you ask your IDE to give you equals and hashCode implementations, and yeah sure whatever just use all the fields. And then, later on, you need some sort of lookup table that cross-references the data modeled by this bean with some outside source of information. So of course that's a HashMap. And then you go through your objects and update them all based on that information. Maybe you just edit the description or the lastUsed field, who knows. All sorts of possibilities here. In any case, there's your bug.