code: public static void listAllVoices() {
          System.out.println();
          System.out.println("All voices available:");
          VoiceManager voiceManager = VoiceManager.getInstance();
          Voice[] voices = voiceManager.getVoices();
          for (int i = 0; i < voices.length; i++) {
              System.out.println("    " + voices[i].getName()
                      + " (" + voices[i].getDomain() + " domain)");
          }
      }
docs: Example of how to list all the known voices.