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Method overriding in Java

Method overriding in Java is a concept based on polymorphism OOPS concept which allows programmer to create two methods with same name and method signature on interface and its various implementation and actual method is called at runtime depending upon type of object at runtime.


1) First and most important rule regarding method overriding in Java is that you can only override method in sub class. You can not override method in same class.


2) Second important rule of method overriding in Java that name and signature of method must be same in Super class and Sub class or in interface and its implementation.


3) Third rule to override method in Java is that overriding method can not reduce accessibility of overridden method in Java. For example if overridden method is public than overriding method can not be protected, private or package-private; But opposite is true overriding method can increase accessibility of method in Java, i.e. if overridden method is protected than overriding method can be protected or public.


4) Another worth noting rule of method overriding in Java is that overriding  method can not throw checked Exception which is higher in hierarchy than overridden method. Which means if overridden method throws IOException than overriding method can not throw java.lang.Exception in its throws clause because java.lang.Exception comes higher than IOException in Exception hierarchy. This rule doesn't apply to RuntimeException in Java, which is not even need to be declared in throws clause in Java.


5) You can not override private, static and final method in Java. private and static method are bonded during compile time using static binding in Java  and doesn't resolve during runtime. overriding final method in Java is compile time error. Though private and static method can be hidden if you declare another method with same and signature in sub class.


6) Overridden method is called using dynamic binding in Java at runtime based upon type of Object. As shown in following example of method overloading.


7) If you are extending abstract class or implementing interface than you need to override all abstract method unless your class is not abstract. abstract method can only be used by using method overriding.


8) Always use @Override annotation while overriding method in Java. Though this is not rule but its one of the best Java coding practice to follow. From Java 6 you can use @Override annotation on method inherited from interface as well.



 * Java program to demonstrate how to override method in Java.

 * Overridden method are resolved during runtime based upon type of object


 * @author Javin


public class CollectionTest {


    public static void main(String args[]) {


      Runnable task = new Task();; //call overridden method in Task


      task = new PeriodicTask();; //calls overridden method in PeriodicTas







class Task implements Runnable{



    public void run() {

        System.out.println("Run method overridden in Task class");





class PeriodicTask extends Task{



    public void run() {

        System.err.println("overridden method run() in PeriodicTask class");





Run method overridden in Task class

overridden method run() in PeriodicTask class

Inheritance examples


HashSet extends AbstractSet , LinkedHashSet extends HashSet, ArrayList extends AbstractList etc.

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