Using Java ruleSet properly

Considering this piece of code

for (MyRule cr : cr开发者_开发问答List) {    
  if (crIds.contains(cr.getParentId())) {
    ruleSet.add(cr);

    for (int cursor = 0; cursor < parentChildrenList.size(); cursor++) {
      if (parentChildrenList.get(cursor).getId().equals(cr.getParentId())) {
        parentChildrenList2.get(cursor).setChildRules(ruleSet);
        parentChildrenList2.remove(cursor + 1);
      }
    }
  }
  ruleSet.clear();
}

When I do the ruleSet.clear() I also lose the value I previously set in parentChildrenList2.get(cursor).setChildRules(ruleSet);

How can I stop losing it but in the same time clearing the ruleSet?

Note that setChildRules() (probably) doesn't create a copy of the Set referenced by ruleSet. It simply copies ("remembers") the reference to that Set. If you later modify that Set (such as calling clear()) then this will be visible to everyone who has a reference to that Set.

It seems like you want each element in parentChildrenList2 to have its own Set. So you effectively need to replace ruleSet.clear() with ruleSet = new HashSet() (or whatever type you used).