docs: public static BackportedJsonStringEncoder getInstance() {
          SoftReference<BackportedJsonStringEncoder> ref = _threadEncoder.get();
          BackportedJsonStringEncoder enc = (ref == null) ? null : ref.get();
  
          if (enc == null) {
              enc = new BackportedJsonStringEncoder();
              _threadEncoder.set(new SoftReference<BackportedJsonStringEncoder>(enc));
          }
          return enc;
      }