Create a directory called "dumb". Put the following file in there:

---- dumb/Pair.java ----
package dumb;
 
public
class Pair
{
   protected Object k;
   protected Object v;
 
   Pair(Object kk, Object vv)
   {
      k = kk;
      v = vv;
   }
}
---- end ----

Put the following file in the current directory:

---- simple.java ----
import dumb.Pair;
 
class simple
{
   simple()
   {
      Pair p = new Pair((Object) new String("a"), (Object) new String("b"));
   }
}
---- end ----

Now try to compile simple.java. When I do so, I get the following error from javac:

----
$ javac simple.java
simple.java:7: No constructor matching Pair(java.lang.Object, java.lang.Object) found in class dumb.Pair.
      Pair p = new Pair((Object) new String("a"), (Object) new String("b"));
               ^
1 error
----

This does not make any sense, as far as I can tell. The compiler is failing to pick up the
Pair(Object, Object) constructor in dumb/Pair.java; this even happens if I fully qualify
every instance of Pair in simple.java (rewriting each as dumb.Pair).

Note, however, that if I delete the package declaration from the beginning of
dum/Pair.java, move that file into the current directory, get rid of the leading "dumb."
from the import statement in simple.java, and recompile, javac works happily.

I don't see anything in the October 31 draft of the Java language reference that might
explain this behaviour, so I conclude for now that it is a serious bug in the compiler.