$ 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