User querry on existing bug

Question

Hi -
A while back I submitted a bug to this forum, and Neal aknowledged the bug, but said the
fix probably would not make it into Tiger. With the JDK1.5RC now here, the bug is not fixed.
The bug is this:
public class XXX<T extends Enum<T> & SomeInterface>
will not compile because the compiler says, "classes cannot directly extend java.lang.Enum"
To me this seems like a fundamental bug in the compiler implementation, and furthermore, if you
are designing an API in which the user must supply an Enum type with certain "capabilities", you can't.
I would like to know if other people consider this a serious bug, or if not, why not?
-Eric

Answer 1

Supose you want the user to supply a set of Token
types. Associated with
each token type could be a regular expression. An
Enum that implents an
interface that has the method getRegEx() would fit the
bill quite nicelty.
Remember when you are working with Enums you can use
EnumMaps and EnumSets
which are more efficient that plain Maps and plain
Sets.
So whenever you want the user to supply your API with
a finite set of
things with each thing having something associated
with it, and Enum
icould be a nice clean way to go.Please excuse me if I don't understand your question correctly. Does the following example fit in your scheme?
package test;
import java.util.Set;
import java.util.EnumSet;
public class EnumsTest {
    public static void main(String args[]) {
        Set<LowerCasedRegularExpresions> s1 = EnumSet.of(
            LowerCasedRegularExpresions.A,
            LowerCasedRegularExpresions.C);
        GenericAlgorithm<LowerCasedRegularExpresions> ga1 = new GenericAlgorithm<LowerCasedRegularExpresions>();
        ga1.execute(s1);
        Set<UpperCasedRegularExpresions> s2 = EnumSet.of(
            UpperCasedRegularExpresions.B,
            UpperCasedRegularExpresions.D);
        GenericAlgorithm<UpperCasedRegularExpresions> ga2 = new GenericAlgorithm<UpperCasedRegularExpresions>();
        ga2.execute(s2);
interface RegularExpresion {
    public String getRegularExpresion();
enum LowerCasedRegularExpresions implements RegularExpresion {
    A {public String getRegularExpresion() {return "a";}},
    B {public String getRegularExpresion() {return "b";}},
    C {public String getRegularExpresion() {return "c";}},
    D {public String getRegularExpresion() {return "d";}};
    public abstract String getRegularExpresion();
enum UpperCasedRegularExpresions implements RegularExpresion {
    A {public String getRegularExpresion() {return "A";}},
    B {public String getRegularExpresion() {return "B";}},
    C {public String getRegularExpresion() {return "C";}},
    D {public String getRegularExpresion() {return "D";}};
    public abstract String getRegularExpresion();
class GenericAlgorithm<K extends RegularExpresion> {
    public void execute(Set<K> set) {
        int i = 0;
        for (K op : set) {
            System.out.print(i++ > 0 ? ", " : "");
            System.out.print(op.getRegularExpresion());
        System.out.println();
}Seriously, I don't see any advantages of this type of programming.
Best regards,
Andrej