1. Overriding method can not be more restrictive than the overridden method.
reason : in case of polymorphism , at object creation jvm look for actual runtime object. jvm does not look for reference type and while calling methods it look for overridden method.
If by means subclass were allowed to change the access modifier on the overriding method, then suddenly at runtime—when the JVM invokes the true object's version of the method rather than the reference type's version then it will be problematic
2. In case of subclass and superclass define in different package, we can override only those method which have public or protected access.
3. We can not override any private method because private methods can not be inherited and if method can not be inherited then method can not be overridden.