Java集合用于层次结构显示？

Question

我正在尝试找到一种方法来使用表中的当前数据结构创建 Assets 管理报告:

Company_Name      Company_id      Managing_Company_id

Target             002             150
Coles              003             150
Wesfarmers         150             100
Shell              001             150
Max Company X      100             null
Woolworths Group   250             100
Caltex             201             250
Woolworths         202             250
Aldi               300             null
PGX                650             600   

报告会将其迭代到层次结构中

Max Company X
             Wesfarmers
                             Target
                             Coles
                             Shell
             Woolworths Group
                             Caltex
                             Woolworths
Aldi
PGX

是否有一个集合可以让我管理这个结构？

Answer 1

乍一看，我正在考虑使用图形/树来处理您的情况的拓扑排序，但当我正在实现一个解决方案时。我认为仅使用 double 映射来记录关系来解决您的问题并不是那么必要:

1. id和name之间的关系；
2. 管理与被管理之间的关系；

然后我们可以得到一个解决方案:

public static void main(String args[]) {
    List<List<String>> listList = prepareTestData();
    Map<String, String> idNameMap = new HashMap<>();
    Map<String, String> managingRelationMap = new HashMap<>();
    List<String> theTop = new ArrayList<>();
    for (List<String> list : listList) {
        idNameMap.put(list.get(1), list.get(0));
        if (list.get(2) == null || list.get(2).equals(list.get(1))) { // no managing or managed by itself;
            theTop.add(list.get(1));
        } else {
            managingRelationMap.put(list.get(1), list.get(2));
        }
    }

    // add specials whose managing does not exist;
    for (String s : managingRelationMap.keySet()) {
        if (!idNameMap.containsKey(managingRelationMap.get(s))) {
            theTop.add(s);
        }
    }

    for (String top : theTop) {
        printManagingStructure(top, managingRelationMap, idNameMap, 1);
    }
}

private static List<List<String>> prepareTestData() {
    List<List<String>> listList = new ArrayList<>();
    listList.add(new ArrayList<>(Arrays.asList("Target", "002", "150")));
    listList.add(new ArrayList<>(Arrays.asList("Coles", "003", "150")));
    listList.add(new ArrayList<>(Arrays.asList("Wesfarmers", "150", "100")));
    listList.add(new ArrayList<>(Arrays.asList("Shell", "001", "150")));
    listList.add(new ArrayList<>(Arrays.asList("Max Company X", "100", null)));
    listList.add(new ArrayList<>(Arrays.asList("Woolworths Group", "250", "100")));
    listList.add(new ArrayList<>(Arrays.asList("Caltex", "201", "250")));
    listList.add(new ArrayList<>(Arrays.asList("Woolworths", "202", "250")));
    listList.add(new ArrayList<>(Arrays.asList("Aldi", "300", null)));
    listList.add(new ArrayList<>(Arrays.asList("PGX", "650", "600")));
    return listList;
}

private static void printManagingStructure(String managingId, Map<String, String> managingRelationMap,
                                           Map<String, String> idNameMap, int gapCount) {
    System.out.println(String.format("%" + gapCount * 20 + "s%-20s", "", idNameMap.get(managingId)));
    if (!managingRelationMap.containsValue(managingId)) {
        return;
    }
    managingRelationMap.entrySet().stream().filter(entry -> entry.getValue().equals(managingId))
            .forEach(entry -> {
                printManagingStructure(entry.getKey(), managingRelationMap, idNameMap, gapCount + 1);
            });
}

输出将是:

                Max Company X       
                                    Wesfarmers          
                                                        Shell               
                                                        Target              
                                                        Coles               
                                    Woolworths Group    
                                                        Caltex              
                                                        Woolworths          
                Aldi                
                PGX