Static, Overriding and Hiding Puzzles

40 min · Intermediate

Back to syllabus (Output Prediction & Debugging Rounds)

Inheritance puzzles come down to one question: is the choice made at compile time from the variable's declared type, or at runtime from the real object? Only instance methods are chosen at runtime. Static methods, fields and overloads are all chosen at compile time.

Topics in this lesson

Static method hiding vs instance overriding
Field hiding: fields are not polymorphic
A constructor calling an overridden method
Initialization order across parent and child
Static counter shared across instances

Interview questions this lesson answers

With Parent p = new Child(); and an overridden instance method show(), which show() runs?
What is method hiding?
Does @Override on a static method in the child compile?
Parent p = new Child(); p.staticMethod() — which version runs?
Can a static method in the child hide an instance method of the parent?
Are fields polymorphic in Java?
How do you access a hidden parent field from the child?
Why should constructors not call overridable methods?
What does a parent constructor see when it calls an overridden method that reads a child field?
What is the order of initialization when you create a child object?

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