我有以下代碼，它是較長(zhǎng)代碼段的一部分，旨在將對(duì)象圖轉(zhuǎn)換為平面樹(shù)，以便現(xiàn)有代碼可以進(jìn)一步處理該樹(shù)：private void addProjectStreamsFromGraphToTree(String parentIndex, Map<String, Object> objectTree, ProjectTreeView projectTreeView) {        Set<Integer> allConnectedLevelOids = new HashSet<Integer>();        // Set in the tree + add everything underneath projectStream:        int index = 1;        String treeIndex ="";        for (Iterator<ExportableProjectStreamView> iter = projectTreeView.getProjectStreamList().iterator(); iter.hasNext(); index++) {            // Getting the concurrentModificationException on the below line            ProjectStreamView projectStreamView = (ProjectStreamView) iter.next();            treeIndex = parentIndex + "." + index;            objectTree.put(treeIndex, projectStreamView);            addLifeCyclesFromGraphToTree(allConnectedLevelOids, projectStreamView , treeIndex, objectTree, projectTreeView);        }    }private void addLifeCyclesFromGraphToTree(Set<Integer> allConnectedLevelOids, ProjectStreamView projectStreamView, String parentIndex, Map<String, Object> objectTree, ProjectTreeView projectTreeView) {    int index = 1;    String treeIndex ="";    ExportableLifecycleView lifecycleView = projectTreeView.getLifecycleList().stream().filter(lcv -> projectStreamView.getLifecycleOid().equals(lcv.getOid())).findFirst().get();    treeIndex = parentIndex + "." + index;    objectTree.put(treeIndex, lifecycleView);    // add the levels that are linked to this lifecycle and at once add all oids of the levels,    // connected to this lifecycle, to the allconnectedLevelOids.           allConnectedLevelOids.addAll(addConnectedLevelsFromGraphToTree(lifecycleView, treeIndex, objectTree, projectTreeView));}如您所見(jiàn)，除了獲取迭代器外，我從不與 projectTreeView.getProjectStreamList() 交互，而且我從不在任何列表上調(diào)用 .remove() 或 .add()。我所做的唯一改變事物的事情是樹(shù)圖上的 put() 和本地 HashSet() 上的 .add。我也不以任何方式更改原始 projectTreeView，并且我只讀取使用迭代器檢索的 projectStreamView 的屬性。