When you hear the word “inheritance,” code may not be the first thing that springs to mind; you’re probably more likely to think of inheriting genetic traits, like eye color from your mother or a smile from your grandfather. But inheritance is also an important feature of object-oriented programming in Java.
Suppose we are building a
Shape class in Java. We might give it some points in 2D, a method for calculating the area, and another method for displaying the shape. But what happens if we want a class for a triangle that has some triangle-specific methods? Do we need to redefine all of the same methods that we created for
No! (Phew.) Lucky for us, a Java class can also inherit traits from another class. Because a
Triangle is a
Shape, we can define
Triangle so that it inherits fields and methods directly from
Shape. A reference of type
Shape can refer to an object of
Shape or an object of
Triangle. The object-oriented principle of inheritance saves us the headache of redefining the same class members all over again.
Triangle class will inherit all the traits of
Triangle can also contain its own unique methods and variables. For example, we could have an instance variable called
hypotenuse and a method called
findHypotenuse() that can only be accessed by
Triangle class references. Objects of
Triangle can call any method contained in
Shape. This gives us a bunch of possibilities!
There are several terms you’ll encounter frequently:
- Parent class, superclass, and base class refer to the class that another class inherits from (like
- Child class, subclass, and derived class refer to a class that inherits from another class (like
Take a look at the image to see how inheritance works in object-oriented programming.