Inheritance

Inheritance

1. Defined as a relationship between objects that share characteristics

   • I.e. -- a new class, aka subclass, is created from an existing class (superclass) by absorbing its state and behavior.
     • The subclass INHERITS characteristics of its superclass.
   • In code, the relationship is specified in the declaration of the subclass, using the keyword "extends".

2. Works by hierarchy

   • See the following chart:
     • Person
       • Student
         • GradStudent
         • UnderGrad
       • Employee
     • The relationship between classes is called an "is-a" relationship.
   • Subclasses can only inherit from a superclass. Subclass cannot inherit from another subclass, and a superclass cannot inherit from a subclass.
     • A subclass may inherit the public/protected variables and methods of its superclass, as well as have additional methods and instance variables not in the superclass as well.
       • Subclasses can redefine the method it inherits as well.
         • I.E. Gradstudent and undergrad may use different algorithms for computing the course grade by changing the computeGrade method inherited from Student.