Overriding and Overloading

• Methods can be overridden or overloaded; constructors can be overloaded but not overridden.
• Abstract methods must be overridden by the first concrete (non-abstract) subclass.
• With respect to the method it overrides, the overriding method
• Must have the same argument list.
• Must have the same return type, except that as of Java 5, the return type can be a subclass—this is known as a covariant return.
• Must not have a more restrictive access modifier.
• May have a less restrictive access modifier.
• Must not throw new or broader checked exceptions.
• May throw fewer or narrower checked exceptions, or any unchecked exception.
• final methods cannot be overridden.
• Only inherited methods may be overridden, and remember that private methods are not inherited.
• A subclass uses super.overriddenMethodName() to call the superclass version of an overridden method.
• Overloading means reusing a method name, but with different arguments.
• Overloaded methods
• Must have different argument lists
• May have different return types, if argument lists are also different
• May have different access modifiers
• May throw different exceptions
• Methods from a superclass can be overloaded in a subclass.
• Polymorphism applies to overriding, not to overloading.
• Object type (not the reference variable's type), determines which overridden method is used at runtime.
• Reference type determines which overloaded method will be used at compile time.