Covariant return type

A covariant return type means changing a method's return type when overriding it in a subclass. Covariant return types were allowed in the Java language since the release of JDK5.0. I will try to illustrate the use of covariant return type using the following example.

class A
{
public List test()
{
return null;
}
}
class B extends A
{
public ArrayList test()
{
return new ArrayList();
}
}
Here we can see that the return type of the method test() in subclass B is the subclass of the return type of method test() in the superclass A.