Inheritance

Inheritance is the property of inheriting the properties from one class to another class. It represents a parent-child relationship

The class that inherits the properties (child class) is called a subclass. A subclass can also have its methods and the private methods of the superclass cannot be inherited by the subclass

The class whose properties are inherited (parent class) is called superclass

Advantages of inheritance

> The main advantage of implementing inheritance is code reusability which means we can reuse the fields and methods of the existing class when we create a new class

> It can be used for method overloading which means calling a method in the child class that is already present in the parent class, in this case child class version of the method is executed

Syntax for inheritance

class Subclass-name extends Superclass-name

{

//methods and fields

}

Where extends is a keyword

Types of inheritance

Single inheritance

Single inheritance inherits the features of one superclass. In the image below, the class Student serves as a superclass for the sub-class Teacher.

SingleInheritance

Program

class Man {
    void name() {
        System.out.println("My name is Paul");
    }
}
class Employee extends Man {
    void age() {
        System.out.println("My age is 42");
    }
}
public class TestInheritance {
    public static void main(String args[]) {
        Employee e = new Employee();
        e.name();
        e.age();
    }
}

In the above use case, man is the superclass and employee is the subclass

Multilevel Inheritance

In multilevel inheritance, a subclass can be inherited by another class. Consider the below diagram Teacher is a subclass that inherits the base class Student whereas Teacher is inherited by Parents but Parents cannot access the features of Student

Multilevel Inheritance

Program

class Man {
    void name() {
        System.out.println("My name is Paul");
    }
}
class Employee extends Man {
    void age() {
        System.out.println("My age is 24");
    }
}
class PersonalInfo extends Employee {
    void address() {
        System.out.println("My address ");
    }
}
public class TestInheritance2 {
    public static void main(String args[]) {
        PersonalInfo p = new PersonalInfo();
        p.name();
        p.age();
        p.address();
    }
}

Hierarchical Inheritance

In hierarchical inheritance a base class can be extended by more than one subclass

HieraricalInheritance

Program

class Man {
    void name() {
        System.out.println("My name is Paul");
    }
}
class Employee extends Man {
    void age() {
        System.out.println("My age is 24");
    }
}
class Student extends Man {
    void department() {
        System.out.println("My department is Sociology");
    }
}
class TestInheritance {
    public static void main(String args[]) {
        Student s = new Student();
        s.name();
        s.department();
//s.ags();//Complier Error
    }
}

Multiple Inheritance

MultipleInheritance

To reduce the complexity of the language, multiple inheritances are not supported by Java. For example, Teachers and Parent classes have methods with the same name and if the method is invoked in subclass Student then there will be a contradiction in invoking the method and a compile-time error will occur.

Inheritance

Advantages of inheritance

Types of inheritance

Single inheritance

Multilevel Inheritance

Hierarchical Inheritance

Multiple Inheritance

Related Tutorials

Related Tutorials

Inheritance

Advantages of inheritance

Types of inheritance

Single inheritance

Multilevel Inheritance

Hierarchical Inheritance

Multiple Inheritance

Related Tutorials

Related Tutorials

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