Java树结构递归生成效率低下如何优化？

心靈之曲 2025-03-04 00:00:00 次阅读

深度剖析树结构递归优化策略

祖传代码中使用递归生成树结构数据，效率低下，本文将针对以下java代码片段进行优化，提升树结构生成效率。

public list creategrouptreenode() {
    list childrenlist = new arraylist();
    getchildlist(0l,childrenlist);
    list treelist = new arraylist();
    map map = new hashmap();
    map.put("id", 0);
    map.put("text","根节点");
    map.put("isleaf", "0");
    map.put("icon", "fa fa-folder");
    map submap = new hashmap();
    submap.put("opened", true);
    submap.put("selected", true);
    map.put("state", submap);
    map.put("children", childrenlist);
    treelist.add(map);
    return treelist;  
}

public list getchildlist(long id,list childrenlist){
    list childlist = basemapper.childlistbyparentid(id);
    if(childlist != null && childlist.size() > 0){
        list tempmap = new arraylist();
        for(int i = 0; i < childlist.size(); i++){
            list mylist = getchildlist(childlist.get(i).getid(),childrenlist);
            map map = new hashmap();
            if(mylist == null){
                map.put("id", childlist.get(i).getid());
                map.put("text", childlist.get(i).getnumber() + " - " + childlist.get(i).getname());
                map.put("isleaf", "1");
                map.put("icon", "fa fa-folder");
                map submap = new hashmap();
                submap.put("opened", false);
                map.put("state", submap);
                tempmap.add(map);
            }else{
                map.put("id", childlist.get(i).getid());
                map.put("text", childlist.get(i).getnumber() + " - " + childlist.get(i).getname());
                map.put("isleaf", "0");
                map.put("icon", "fa fa-folder");
                map.put("children", mylist);
                map submap = new hashmap();
                submap.put("opened", false);
                map.put("state", submap);
                tempmap.add(map);
            }
            if(id == 0){
                childrenlist.add(map);
            }
        }
        return tempmap;
    }
    return null;
}

这段代码中getchildlist方法存在效率问题。首先，childrenlist参数作为输出参数，仅在id == 0l时使用，这导致了不必要的参数传递。我们可以直接利用该方法的返回值，移除该参数。

其次，在getchildlist方法的循环中，反复调用childlist.get(i)降低了效率。我们可以引入一个中间变量缓存循环中的元素，或者使用增强型for循环来优化。

最后，在for循环内的if分支中，大部分代码是相同的，只有isleaf和children字段有所不同，我们可以将重复的代码提取出来，只处理差异部分。

经过优化后的代码如下：

public List createGroupTreeNode() {
    List childrenList = getChildList(0L);
    // ....
}

public List getChildList(Long id) {
    List childList = baseMapper.childListByParentId(id);
    if(childList != null && childList.size() > 0){
        List tempMap = new ArrayList();
        for (BaseGroup it : childList) {
            Map map = new HashMap();
            map.put("id", it.getId());
            map.put("text", it.getNumber() + " - " + it.getName());
            map.put("icon", "fa fa-folder");
            Map subMap = new HashMap();
            subMap.put("opened", false);
            map.put("state", subMap);

            List mylist = getChildList(it.getId());
            if (mylist == null) {
                map.put("isleaf", "1");
            } else {
                map.put("isleaf", "0");
                map.put("children", mylist);
            }
            tempMap.add(map);
        }
        return tempMap;
    }
    return null;
}