Whenever you inherit/extend a class, a copy of superclass’s members is created in the subclass object and thus, using the subclass object you can access the members of both classes.
Example
In the following example we have a class named SuperClass with a method with name demo(). We are extending this class with another class (SubClass).
Now, you create an object of the subclass and call the method demo().
class SuperClass{ public void demo() { System.out.println("demo method"); } } public class SubClass extends SuperClass { public static void main(String args[]) { SubClass obj = new SubClass(); obj.demo(); } }Output
demo methodSuper class’s Constructor in inheritance
In inheritance constructors are not inherited. You need to call them explicitly using the super keyword.
If a Super class have parameterized constructor. You need to accept these parameters in the sub class’s constructor and within it, you need to invoke the super class’s constructor using “super()” as −
public Student(String name, int age, String branch, int Student_id){ super(name, age); this.branch = branch; this.Student_id = Student_id; }Example
Following java program demonstrates how to call a super class’s constructor from the constructor of the sub class using the super keyword.
class Person{ public String name; public int age; public Person(String name, int age){ this.name = name; this.age = age; } public void displayPerson() { System.out.println("Data of the Person class: "); System.out.println("Name: "+this.name); System.out.println("Age: "+this.age); } } public class Student extends Person { public String branch; public int Student_id; public Student(String name, int age, String branch, int Student_id){ super(name, age); this.branch = branch; this.Student_id = Student_id; } public void displayStudent() { System.out.println("Data of the Student class: "); System.out.println("Name: "+this.name); System.out.println("Age: "+this.age); System.out.println("Branch: "+this.branch); System.out.println("Student ID: "+this.Student_id); } public static void main(String[] args) throws CloneNotSupportedException { Person person = new Student("Krishna", 20, "IT", 1256); person.displayPerson(); } }Output
Data of the Person class: Name: Krishna Age: 20
Updated on 01-Aug-2019 12:09:16
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Main Content
Superclass Relation to Subclass
Subclasses can override superclass methods to support the greater specialization defined by the subclass. Because of the relationship that a subclass object is a superclass object, it is often useful to call the superclass version of the method before executing the specialized subclass code.
How to Call Superclass Methods
Subclass methods can call superclass methods if both methods have the same name. From the subclass, reference the method name and superclass name with the @ symbol.
This is the syntax for calling a superMethod defined by MySuperClass:
superMethod@MySuperClass(obj,superMethodArguments)
For example, a subclass can call a superclass disp method to implement the display of the superclass part of the object. Then the subclass adds code to display the subclass part of the object:
classdef MySub < MySuperClass methods function disp(obj) disp@MySuperClass(obj) ... end end end
How to Call Superclass Constructor
If you create a subclass object, MATLAB® calls the superclass constructor to initialize the superclass part of the subclass object. By default, MATLAB calls the superclass constructor without arguments. If you want the superclass constructor called with specific arguments, explicitly call the superclass constructor from the subclass constructor. The call to the superclass constructor must come before any other references to the object.
The syntax for calling the superclass constructor uses an @ symbol:
obj = obj@MySuperClass(SuperClassArguments)
In this class, the MySub object is initialized by the MySuperClass constructor. The superclass constructor constructs the MySuperClass part of the object using the specified arguments.
classdef MySub < MySuperClass methods function obj = MySub(arg1,arg2,...) obj = obj@MySuperClass(SuperClassArguments); ... end end end
See Subclass Constructors for more information.
Related Topics
- Modify Inherited Methods