OOP AND ENCAPSULATION

Instance Methods vs Variables and Static Methods

Rule: Instance methods are overridden, while variables and static methods are hidden.

The method invoked depends on the actual object type (runtime)
The field accessed depends on the reference type (compile-time)

class Parent {
    String role = "Parent";
    static String familyName() { return "Smith"; }
    String introduce() { return "I am a Parent"; }
}

class Child extends Parent {
    String role = "Child";                      // Field hiding
    static String familyName() { return "Johnson"; }  // Method hiding
    String introduce() { return "I am a Child"; }     // Method overriding
}

Parent member = new Child();
System.out.println(member.role);        // Parent (field access - compile-time)
System.out.println(member.familyName()); // Smith (static method - compile-time)
System.out.println(member.introduce());  // I am a Child (instance method - runtime)

💡 Learning Tip: Remember “HIDE vs OVERRIDE” - static methods and fields are HIDDEN (reference type matters), instance methods are OVERRIDDEN (object type matters).

Q: Does overriding a method replace the original method call even if the reference is of parent type?
A: Yes — overridden instance methods use the object type at runtime (dynamic dispatch). Static methods use the reference type (they are hidden, not overridden).