Type Safety Violation: Casting a superclass reference to a subclass violates type safety, which is a fundamental principle of object-oriented programming. Type safety ensures that objects are only used in ways that are consistent with their declared types. By casting a superclass reference to a subclass, you are bypassing the type checking mechanism and allowing the object to be used in ways that may not be intended or supported.
Unexpected Behavior: Casting a superclass reference to a subclass can lead to unexpected behavior because the subclass may have additional methods or properties that are not present in the superclass. When you access these additional members through the superclass reference, you may encounter runtime errors or unpredictable behavior.
NullPointerExceptions: Casting a superclass reference to a subclass can result in a NullPointerException if the subclass instance is null. This is because the superclass reference does not have access to the subclass-specific methods and properties, including the ability to check for null. If you try to access a member of a null subclass instance, you will get a NullPointerException.
Loss of Subclass Functionality: Casting a superclass reference to a subclass can cause you to lose access to subclass-specific functionality. This is because the superclass reference can only access the members that are declared in the superclass. Any methods or properties that are defined in the subclass will be inaccessible through the superclass reference.
To avoid these potential dangers, it is generally recommended to use polymorphism and method overriding instead of casting superclass references to subclasses. Polymorphism allows you to write code that can work with objects of different subclasses without having to worry about casting. Method overriding ensures that subclasses can provide their own implementations of methods inherited from the superclass, without breaking the type safety of the program.