Java collections. Why no Primiti

The problem with primitive types (at least until Java 5) is that they didn't extend from the base Object class. All of the collections need to specify a class for all the methods they are using - and they specify Object, since Object is the base of all the classes.

As of Java 5, you will find that Java will implicitly switch between a primitive and it's corresponding wrapper class when you need it. This means you can add an int, or a double, etc. to a Collection. The VM will automatically wrap the primitive in a wrapper class for you and place the wrapper in the Collection.