[Java] 객체가 비어있는지 확인

public static Boolean empty(Object obj) {
  if (obj instanceof String) return obj == null || "".equals(obj.toString().trim());
  else if (obj instanceof List) return obj == null || ((List) obj).isEmpty();
  else if (obj instanceof Map) return obj == null || ((Map) obj).isEmpty();
  else if (obj instanceof Object[]) return obj == null || Array.getLength(obj) == 0;
  else return obj == null;
 }