A subclass changing the behavior of a method it inherited from its super class is called as Method Overriding.
While overriding a method, a subclass must define it with the same set of method parameters and return type as present in its super class.
package com.techstackjournal.methodoverriding;
public class Shape {
public void draw(int thickness) {
System.out.println("Preparing the canvas...");
}
}package com.techstackjournal.methodoverriding;
public class Rectangle extends Shape {
public void draw(int thickness) {
System.out.println("Drawing Rectangle...");
}
public void draw(int thickness, String fillColor) {
System.out.println("Drawing Rectangle and Filling Color...");
}
}package com.techstackjournal.methodoverriding;
public class Application {
public static void main(String[] args) {
Rectangle rectangle = new Rectangle();
rectangle.draw(1);
}
}Drawing Rectangle...- Here, we are overriding draw method of Shape class in Rectangle class by implementing it again in Rectangle class
- Calling the draw method using Rectangle reference variable invokes draw method of Rectangle class
Advantages of Method Overriding:
- Method overriding will allow the subclass to define the method that is specific to the subclass
- By overriding a method instead of creating a new method a subclass can get benefits of Polymorphism
Points to Remember
Rules of Method Overriding:
- A subclass must maintain the same set of method arguments and return type
- If the return type is a class, then the return type can be a sub class of super class return type
- A subclass cannot reduce the visibility of the inherited method from super class. That means, overriding a public method in super class as a private method in subclass is not legal
- A subclass can override a method only when that method is visible to it.
- If a subclass define a method with the same signature as of super class which has defined it as private, we do not call it as overriding.
- You can increase the visibility of an inherited method from super class. That means, a protected method in super class can be defined as a public method in subclass.
- A subclass cannot override a final method
- A subclass cannot override a static method
- Some additional rules related to exceptions, which we will see in later sections
- A subclass cannot throw a broader exception than what is declared in the super class
- But it can throw a narrower exception
- Overriding method can throw any runtime exception, even if it is not defined in its declaration in super class
