@Override
          public int compare(Constant a, Constant b) {
            int ret;
            ret = countUses.get(b) - countUses.get(a);

            if (ret == 0) {
              /*
               * Provide sorting determinisim for constants with same
               * usage count.
               */
              ret = a.compareTo(b);
            }

            return ret;
          }
Gets all of the collectable constant values used in this method, sorted by most used first.
Skips non-collectable consts, such as non-string object constants

@return {@code non-null;} list of constants in most-to-least used order
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/ConstCollector.java