static S structureToJava(O o) {
  if (o == null) ret "null";
  if (o instanceof Bool || o instanceof Number) ret str(o);
  if (o instanceof S) ret quote(o);
  if (o instanceof LinkedHashMap) ret structureToJava_map("litorderedmap", o);
  if (o instanceof HashMap) ret structureToJava_map("litmap", o);
  if (o instanceof TreeMap) ret structureToJava_map("littreemap", o);
  if (o instanceof L)
    ret "ll(" + join(", ", map((L) o, f structureToJava)) + ")";
  fail("boohoo " + className(o));
}

static S structureToJava_map(S type, O o) {
  ret type + "(" + join(", ", mapMapToList((Map) o, func(O a, O b) { structureToJava(a) + ", " + structureToJava(b) })) + ")";
}