Java

Can you override Static Methods in Java?

Question: Can you override Static Methods in Java?

Answer: Well… the answer is NO if you think from the perspective of how an overriden method should behave in Java. But, you don’t get any compiler error if you try to override a static method. That means, if you try to override, Java doesn’t stop you doing that; but you certainly don’t get the same effect as you get for non-static methods. Overriding in Java simply means that the particular method would be called based on the run time type of the object and not on the compile time type of it (which is the case with overriden static methods). Okay… any guesses for the reason why do they behave strangely? Because they are class methods and hence access to them is always resolved during compile time only using the compile time type information. Accessing them using object references is just an extra liberty given by the designers of Java and we should certainly not think of stopping that practice only when they restrict it 🙂
Example: let’s try to see what happens if we try overriding a static method:-


class SuperClass {
	 ......
	public static void staticMethod() {
		System.out.println("SuperClass: inside staticMethod");
	}
	 ......
}

public class SubClass extends SuperClass {
	 ......
	// overriding the static method
	public static void staticMethod() {
		System.out.println("SubClass: inside staticMethod");
	}

	 ......
	public static void main(String[] args) {
		// ......
		SuperClass superClassWithSuperCons = new SuperClass();
		SuperClass superClassWithSubCons = new SubClass();
		SubClass subClassWithSubCons = new SubClass();

		superClassWithSuperCons.staticMethod();
		superClassWithSubCons.staticMethod();
		subClassWithSubCons.staticMethod();
		 ...
	}

}

Output:-

SuperClass: inside staticMethod

SuperClass: inside staticMethod

SubClass: inside staticMethod
Notice the second line of the output. Had the staticMethod been overriden this line should have been identical to the third line as we’re invoking the ‘staticMethod()’ on an object of Runtime Type as ‘SubClass’ and not as ‘SuperClass’. This confirms that the static methods are always resolved using their compile time type information only.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s