code: @Deprecated
      public List<String> getFirstCharactersInScripts() {
          List<String> dest = new ArrayList<String>(200);
          // Fetch the script-first-primary contractions which are defined in the root collator.
          // They all start with U+FDD1.
          UnicodeSet set = new UnicodeSet();
          collatorPrimaryOnly.internalAddContractions(0xFDD1, set);
          if (set.isEmpty()) {
              throw new UnsupportedOperationException(
                      "AlphabeticIndex requires script-first-primary contractions");
          }
          for (String boundary : set) {
              int gcMask = 1 << UCharacter.getType(boundary.codePointAt(1));
              if ((gcMask & (GC_L_MASK | GC_CN_MASK)) == 0) {
                  // Ignore boundaries for the special reordering groups.
                  // Take only those for "real scripts" (where the sample character is a Letter,
                  // and the one for unassigned implicit weights (Cn).
                  continue;
              }
              dest.add(boundary);
          }
          return dest;
      }
docs: Return a list of the first character in each script. Only exposed for testing.
  
  @return list of first characters in each script
  @deprecated This API is ICU internal, only for testing.
  @hide original deprecated declaration
  @hide draft / provisional / internal are hidden on Android