One public method that is defined in the Object class is the toString() method. This means that objects belonging to the subclasses can use the inherited variables and methods as their own.įor example, all Java classes are subclasses of the Object class, which is the most general class in Java’s class hierarchy. In Java, the public and protected instance methods and instance variables of a superclass are inherited by all of its subclasses.

Abstract Classes, Interfaces, and Polymorphism.

Polymorphism and Object-Oriented Design.But how exactly does the concept of inheritance apply to Java (and to other object-oriented languages)? And, more importantly, how do we use the inheritance mechanism in object-oriented design? We have deliberately used an example from the natural world to show that the concept of inheritance in Java is inspired by its counterpart in the natural world. Thus, by virtue of its class’s position in this hierarchy, we can infer that a horse is a living, moving, four-legged vertebrate, which is warm blooded and nurses its young. Some mammals, such as humans and penguins, do not have four legs. Finally, the class of horses is a further specialization over the class of mammals, in that all horses have four legs. Similarly, the class of mammals is a further specialization over the vertebrates in that mammals are warm-blooded and nurse their young.

The class of vertebrates is a somewhat more specialized type of animal, in that vertebrates have backbones. Let’s consider an example of a natural form of inheritance: Just as horses inherit the attributes and behaviors associated with mammals and vertebrates, a Java subclass inherits the attributes and behaviors of its superclasses.Īs shown in the diagram above, the root of the hierarchy, which is always shown at the top, the Animal class contains the most general attributes, such as being alive and being able to move. Class inheritance is the mechanism whereby a class acquires (inherits) the methods and variables of its superclasses. Among the most important concepts in object oriented programming are the concepts of inheritance and polymorphism.

Inheritance in java