private String getBiggestDifference(Map a, Map b) {
private String getBiggestDifference(Map a, Map b, boolean needChange, String lastChangeNode) {
  private String getBiggestDifference(Map a, Map b) {    int diff = 0;    String result = "";    for (Iterator it = a.keySet().iterator(); it.hasNext(); ) {      String node = (String) it.next();      int oldnum = ( (Integer) a.get(node)).intValue(); //how many agents on current node?      int newnum = ( (Integer) b.get(node)).intValue(); //how many agents on this node after balancing?      int x = oldnum - newnum; //get the difference.      if ( (diff == 0 && x != 0) || x > diff) {        diff = x;        result = node;      }    }//logger.info("get current biggest difference: node=" + result + ", difference=" + diff);    return result;  }