Not getting "Add unimplemented methods" error in eclipse

I am working on Selenium with Java and using Listeners.

I created the class, imported the TestNG, and then added method as;

Public class Listener implements ITestListener{
}

I got an error at "ITestListner" and then imported "ITestListner(org.testng). After this it was expected that I will get an error for "Listener" but I didn't get any error.

I tried creating with abstract class but still didn't get the error.

package com.testng;

import org.testng.ITestListener;

public class Listeners implements ITestListener{

}

The expectation is when I move the cursor over "Listeners" I should get "Add unimplemented methods" option.