Bill Pugh writes:

We've been working on tuning the dead store detector, and came across
this
in java.util.UUID:

     /**
      * Static factory to retrieve a type 4 (pseudo randomly generated)
UUID.
      *
      * The <code>UUID</code> is generated using a cryptographically
strong
      * pseudo random number generator.
      *
      * @return a randomly generated <tt>UUID</tt>.
      */
     public static UUID randomUUID() {
         SecureRandom ng = numberGenerator;
         if (ng == null) {
             numberGenerator = ng = new SecureRandom();
         }

         byte[] randomBytes = new byte[16];
         ng.nextBytes(randomBytes);
         randomBytes[6] &= 0x0f; /* clear version */
         randomBytes[6] |= 0x40; /* set to version 4 */
         randomBytes[8] &= 0x3f; /* clear variant */
         randomBytes[8] |= 0x80; /* set to IETF variant */
         UUID result = new UUID(randomBytes);
         return new UUID(randomBytes);
     }



Result of this is that for each call, you create two UUID objects, one
of which is thrown away.

Only a performance penalty, rather than correctness. But still, it
should be fixed.



Bill