Covariant Method Overriding of Java 5 - Coding Best Practices

Sometime knowledge of a specific Java feature can improve code quality, Covariant method overriding is one of such feature. Covariant method overriding was introduced in Java 5, but it seems it lost between other more powerful features of that release. Surprisingly not many Java programmer knows about Covariant overriding, including myself, until I read, one of the best Java book on Collection framework, Java Generics and Collection. Covariant method overriding helps to remove type casting on client side, by allowing you to return subtype of actually return type of overridden method. Covariant overriding can be really useful, while overriding methods which returns object e.g. clone() method. Since clone() return object every client needs to cast on to appropriate subclass, not any more. By using Java 5 covariant overriding, we can directly return subtype instead of object, as we will seen in examples of this article. This feature is not a star feature like Generics or Enum, but it's definitely something worth knowing, given overriding methods are integral part of Java programming. I have discussed a bit about this feature earlier in difference between overriding and overloading article, and here I will show couple of more examples to justify it's usage.

Read more �