$ cat -n Subst.java
     1  class A<T> {
     2      class B {
     3          T returnT() { return null; }
     4          Object returnU() { return null; }
     5      }
     6  }
$ cat -n Subst2.java
     1  class A<T> {
     2      class B<U> {
     3          T returnT() { return null; }
     4          U returnU() { return null; }
     5      }
     6  }
$ cat -n X.java
     1  class X {
     2      A<String>.B y;
     3  }
$ cat -n Y.java
     1  class Y {
     2      X x;
     3      void foo() {
     4          String s = x.y.returnU();
     5      }
     6      public static void main(String... args) {
     7      }
     8  }

Now compile like this:

$ rm *.class
$ javac -sourcepath /xyyz Subst.java X.java Y.java
Y.java:4: incompatible types
found   : java.lang.Object
required: java.lang.String
        String s = x.y.returnU();
                              ^
1 error
$ javac -sourcepath /xyyz Subst2.java Y.java

The last command succeeds indicating that the type variable U got the type String.

###@###.### 2004-11-18 05:34:50 GMT