FULL PRODUCT VERSION :
java version "1.6.0_12"
Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
Java HotSpot(TM) Client VM (build 11.2-b01, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
Linux attemptkind-lx 2.6.27-9-generic #1 SMP Thu Nov 20 21:57:00 UTC 2008 i686 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
If you declare a class which includes a generic type, then try to reference a method of that class which uses an unrelated generic type through an iterative for loop, the compiler declares "incompatible types."

I know that sounds confusing, sorry. Look at the code under the "Source code" section -- it's much clearer in code than in words.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
$ javac isitabug/genericscastfor/Whoa.java
isitabug/genericscastfor/Whoa.java:27: incompatible types
found : java.lang.Object
required: java.lang.String
    for (String one: other.getThingList())
                                       ^
Note: isitabug/genericscastfor/Whoa.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package isitabug.genericscastfor;

import java.util.LinkedList;
import java.util.List;

public class Whoa<T>
{
  public List<String> getThingList ()
  {
    return _stringList;
  }
  
  public void walkStringListOk (Whoa<T> other)
  {
    // this works fine because the generic T is specified
    for (String one: other.getThingList())
    {
      // ...
    }
  }
  
  public void walkStringList (Whoa other)
  {
    // getting generically outside an iterative for loop works fine
    List<String> myList = other.getThingList();
    // getting with an iterative for loop won't compile
    for (String one: other.getThingList())
    {
      // ...
    }
  }
  
  private List<String> _stringList = new LinkedList<String>();
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
There are several workarounds, and they're all pretty obvious:

1) Cast the item you're looping over.
2) Declare the generic type when referencing the base object (Whoa)
3) Don't use the iterative for loop.
... etc.