Advanced Java

Unlike with arrays, it is important to remember with generics that is not possible to upcast an object from its superclass to its subclass. So for example, this will create a compile time error.

Java Code:

import java.util.*;

public class NonCovariantGenerics { 
// Compile Error: incompatible types: 
List<Shape> slist = new ArrayList<Rectangle>();

In this listing List of Rectangle is not type-equivalent to a List of Shape, even if an Rectangle ...

Tags: collections, generics, wildcards

Categories

Generics , Collection