How to get class fields?

I am trying to itterate over public static fields in class with private constructor, but getFields/getDeclaredField returns zeroSize array, so I never so Log messages from loop. Where is an error?
Constants

public final class SyncKeysConstants {
  private SyncKeysConstants() {
  }
  public static final String HOME = "home";

}

Method

public static void updateConnection(Context context) {
    boolean connected = check(context);
    Log.e("updateConnection", " current - " + connected);
    for (Field f : SyncKeysConstants.class.getFields()) {
      Log.e("field", " name - " + f.getName());
      try {
        String value = (String) f.get(null);
        Log.e("field", " name - " + f.getName() + ", data - " + value);
        if (connected) {
          SyncStatus.setNoConnection(context, value, false);
        }
      } catch (IllegalAccessException e) {
        e.printStackTrace();
      }
    }
  }