// Note: This does have the values problem (complicated values can cause memory leaks)
sclass BetterThreadLocal<A> {
  Map<Thread, A> map = newWeakHashMap();
  
  *() {}
  *(A value) { set(value); }
  
  bool isSet() { ret map.containsKey(currentThread()); }
  
  A get() {
    if (map.containsKey(currentThread()))
      ret map.get(currentThread());
    A value = initialValue();
    set(value);
    ret value;
  }
  
  A get(Thread thread) {
    ret thread == null ? null : map.get(thread);
  }
  
  void set(A a) {
    map.put(currentThread(), a);
  }
  
  public A initialValue() { null; }
}

Also this can give you the value for another thread.