java8 集合构造树结构

公共方法

public static <T,V> List<T> buildTree(List<T> list, Function<T, V> idMapper, Function<T, V> pIdMapper,
                                  Function<T, List<T>> getNodeMapper, BiConsumer<T, List<T>> setNodeMapper){
    Map<V,T> vtMap = list.stream().collect(Collectors.toMap((idMapper),(value->value)));

    list.clear();
    for (Map.Entry<V, T> entry : vtMap.entrySet()) {
        T t = entry.getValue();
        V pId = pIdMapper.apply(t);

        if(isValid(pId)){
            T t1 = vtMap.get(pId);
            if(t1 == null){//找不到该父id对应的数据
                continue;
            }
            List<T> nodeList = getNodeMapper.apply(t1);
            if(nodeList == null){
                nodeList = new ArrayList();
                setNodeMapper.accept(t1, nodeList);
            }
            nodeList.add(t);
        } else {
            list.add(t);
        }
    }
    return list;
}

public static <V> boolean isValid(V value){
    boolean flag = false;
    if(null != value && value instanceof String && StringUtils.isNotNull(value)){
        flag = true;
    }
    if(null != value && value instanceof Integer && 0 != ((Integer) value).intValue()){
        flag = true;
    }
    return flag;
}

调用：

dtoList = commTree(dtoList, x->x.getId(), x->x.getParentId(), x->x.getNode(), KnowlCategoryDto::setNode);

注意：给属性赋值只能使用::而无法使用->