Re: generics & enums

On 14-8-2006 20:57, josef wrote:
[...]

[...]

Use Class#getEnumConstants()
<http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Class.html#getEnumConstants()>
Looking at the source code of this method, however, it appears to use
reflection as well, though it caches it's values (so a subsequent calls
of getEnumConstants() return the cached values).
You could apply the same technique. The following example caches the
enum constants immediately in the constructor:

public class A<E extends Enum<E>> {

     private final E[] enumConstants;

     public A(Class<E> enumType) {
         enumConstants = enumType.getEnumConstants();
     }

     public E get(int ordinal) {
         if (ordinal >= 0 && ordinal < size()) {
             return enumConstants[ordinal];
         } else {
             return null;
             // OR:
             // throw new
IndexOutOfBoundsException(String.valueOf(ordinal));
         }
     }

     public int size() {
         return enumConstants.length;
     }

     public static void main(String[] args) {
         A<Thread.State> a = new A<Thread.State>(Thread.State.class);
         for (int i = -1; i <= a.size(); i++) {
             System.out.println("A.get(" + i + ")=" + a.get(i));
         }
     }
}

--
Regards,

Roland