sclass FilesBasedStringMap extends AbstractMap<S> {
  File dir;
  
  *() {}
  *(File *dir) {}
  
  public S get(O a) {
    ret dropFirstLine(loadGZTextFile(fileForKey(a)));
  }
  
  public synchronized Set<Map.Entry<S,S>> entrySet() {
    Set
    for (File f : 
listFiles(dir)) {
      S md5 = md5FromUniqueFile(f);
  }
  
  public put(S a, S b) {
    saveGZTextfile(fileForKey(a), quote(a) + "\n" + b);
  }
  
  public S remove(O a) {
    put(a, null);
  }

  File fileForKey(O key) {
    if (!isString(key)) null;
    ret new File(assertNotNull(dir), uniqueFileNameUsingMD5_80((S) key));
  }
}