13. Method overriding in java


✔ JAVA CHAPTERS:-

1. Introduction to Java
2. Features of Java
3. Java Virtual Machine
4. D/F B/W JVM, JRE, JDK
5. Java Data Types
6. Java Programs
7. Setting Java Path
8. OOPs Concepts
9. Object & Class In Java
10. OOPs Continued
11. Encapsulation & Polymorphism
12. Method Overloading
13. Method Overriding
14. Dynamic Method Dispatch
15. Association In Java
16. Inheritance in Java
17. Aggregation in java
18. Command Line Argument
19. Execute Command Line
20. Read Input From Command Line
21. Abstract Class In Java
22. Interface in Java
23. Cutom Marker Interface
24. Constructor In Java
25. Package in Java
26. Acess Modifier In Java
27. Static Import In Java
28. Package Class In Java
29. This Keyword
30. Instance Intializer Block
31. Super Keyword
32. Static Keyword
33. Final Keyword



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Method overriding in Java

If a subclass provides a method with the same signature (name and parameter) as in its super class, then subclass overrides the method of its super class. This process of overriding a super class method by subclass is known as method overriding.

Conditions for method overriding:

  1. 1. Method in subclass must have same signature as in its super class.
  2. 2. Two classes must follow IS-A relationship.

Example:

/**
 * This program is used for simple method overriding example.
 * @author javatutorialpoint
 */
class Student {
      /**
       * This method is used to show details of a student.
       * @author javatutorialpoint
       */
      public void show(){
            System.out.println("Student details.");
      }
}
 
public class CollegeStudent extends Student {
      /**
       * This method is used to show details of a college student.
       * @author javatutorialpoint
       */
      public void show(){
            System.out.println("College Student details.");
      }
 
      //main method
      public static void main(String args[]){
       CollegeStudent obj = new CollegeStudent();
       //subclass overrides super class method
       //hence method of CollegeStudent class will be called.
       obj.show();
      }
}

Output:

College Student details.

Can static method be overridden?

No, Static methods can’t be overridden because they are associated with class not with the object.

Role of access modifiers in method overriding:

Access modifier of overridden method in subclass can’t be more restrictive than in super class. Otherwise it will throw an exception.

 Example:

/**
 * This program is used for simple method overriding example.
 * @author javatutorialpoint
 */
class Student {
      /**
       * This method is used to show details of a student.
       * @author javatutorialpoint
       */
      public void show(){
            System.out.println("Student details.");
      }
}
 
public class CollegeStudant extends Student {
      /**
       * This method is used to show details of a college student.
       * @author javatutorialpoint
       */
      protected void show(){//compile-time error
            System.out.println("College Student details.");
      }
 
      //main method
      public static void main(String args[]){
       CollegeStudant obj = new CollegeStudant();
       //subclass overrides super class method
       //hence method of CollegeStudant class will be called.
       obj.show();
      }
}

Output:

Exception in thread "main" java.lang.Error: 
Unresolved compilation problem:
Cannot reduce the visibility of the inherited method from Student
at com.javawithease.business.CollegeStudent.show(CollegeStudent.java:22)
at com.javawithease.business.CollegeStudent.main(CollegeStudent.java:30)

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