Calling overridable methods during construction poses a risk of invoking methods on an incompletely constructed object
and can be difficult to discern. It may leave the sub-class unable to construct its superclass or forced to replicate
the construction process completely within itself, losing the ability to call super().
If the default constructor contains a call to an overridable method, the subclass may be completely uninstantiable.
Note that this includes method calls throughout the control flow graph - i.e., if a constructor Foo() calls
a private method bar() that calls a public method buz(), this denotes a problem.
Example :
public class SeniorClass { public SeniorClass(){ toString(); //may throw NullPointerException if overridden } public String toString(){ return "IAmSeniorClass"; } } public class JuniorClass extends SeniorClass { private String name; public JuniorClass(){ super(); //Automatic call leads to NullPointerException name = "JuniorClass"; } public String toString(){ return name.toUpperCase(); } }