The Java Language Specification, Third Edition

8.1.2 Generic Classes and Type Parameters CLASSES
180
T convert();
}
class ReprChange {
T t;
void set(S s) { t = s.convert(); }
S get() { return t.convert(); }
}
Parameterized class declarations can be nested inside other declarations.
DISCUSSION
This is illustrated in the following example:
class Seq {
T head;
Seq tail;
Seq() { this(null, null); }
boolean isEmpty() { return tail == null; }
Seq(T head, Seq tail) { this.head = head; this.tail = tail; }
class Zipper {
Seq zip(Seq that) {
if (this.isEmpty() || that.isEmpty())
return new Seq();
else
return new Seq(
new Pair(this.head, that.head),
this.tail.zip(that.tail));
}
}
}
class Pair {
T fst; S Snd;
Pair(T f, S s) {fst = f; snd = s;}
}
DRAFT
class Client {
{
Seq strs =
new Seq("a", new Seq("b",
new Seq()));
Seq nums =
new Seq(new Integer(1),
new Seq(new Double(1.5),