Odd behavior with type inference

"Mike Schilling" <mscottschilling@hotmail.com>
Sun, 19 Sep 2010 10:25:23 -0700
While constructing the FilteredCollection class, I ran into the following
oddity with type inference. The following class fails to compile (using
javac 1.6.0_20):

import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

public class Oddity<C> implements Iterable<C>
    public Iterator<C> iterator()
        return null;

    public static void main(String[] args)
        List list = Arrays.asList(1, "a", false);
        for (String s : getOddity(list, String.class)) // ******

    public static<T,C> Iterable<C> getOddity(Collection<T> coll, Class<C>
        return null;

The error, at the starred line, is

    incompatible types
    found : java.lang.Object
    required: java.lang.String

That is, it looks as if the inference that getOddity should return an
Iterable<String> fails.

However, it works perfectly if the declaration of "list" in the previous
line is changed to

    List<?> list

What's the deal here? Does the presence of a raw type interfere with type


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