Java untyped generic classes, removing their functions generics types

Question

Ok Question about javas generics, iterable, and for-each loop. The problem being that, if I declare my 'Test' class untyped, I lose all generic information on all my functions and for-each is not likeing that at all.

Example

public class Test<T> implements Iterable<Integer>{

    public Test() {}

    public Iterator<Integer> iterator() {return null;}

    public static void main(String[] args) {
        Test t = new Test();

        //Good,
        //its returning an Iterator<object> but it automatically changes to  Iterator<Integer>
        Iterator<Integer> it = t.iterator();

        //Bad
        //incompatable types, required Integer, found Object
        for(Integer i : t){
        }
    }Untyped generic classes losing 
}

When 'Test t' is untyped, the 'iterator()' function returns 'iterator' instead of a 'iterator < Integer >'.

I'm not exactly sure for the reason behind it, I know a fix for that is just use a wild card on 'Test < ? > t = new test()'. However this is a less than ideal solution.
Is their any way to only edit the class declaration and its functions and have the for each loop work untyped?

Answer 1

You should just do the following:

public class Test implements Iterable<Integer>{

Remove the generic type all together.

Your Test class is not generic at all. It is simply implementing a generic interface. Declaring a generic type is not necessary. This will also have the benefit of remove that generic warning you were getting.

@Eugene makes a good point. If you actually wanted a generic Test type, you should declare Test as a generic iterator:

You should just do the following:

public class Test implements Iterable<Integer>{

Remove the generic type all together.

Your Test class is not generic at all. It is simply implementing a generic interface. Declaring a generic type is not necessary. This will also have the benefit of remove that generic warning you were getting.

public class Test<T> implements Iterable<T>{

And then, make sure you make Test generic when you instantiate it.

Test<Integer> t = new Test<Integer>;

Then calls to for(Integer i: t) will compile.

Answer 2

You should either write this:

public class Test implements Iterable<Integer>{
  ...

or actually generify your class:

public class Test<T> implements Iterable<T> {

    public Iterator<T> iterator() {return null;}

    public static void main(String[] args) {
        Test<Integer> t = new Test<Integer>();

        Iterator<Integer> it = t.iterator();

        for(Integer i : t){
        }
    } 
}