使用许多属性进行 Java 对象比较

Question

我有一些订单需要在配送 route 装载和卸载，一条路线可以指定一个 OrderDocument 供其装载、卸载或同时装载和卸载。 每个订单文档均按分配的 route 的索引进行排序。所以类看起来像这样:

class OrderDocument implements Comparable<ModelTask>{
    int order_id;  // The document ID
    int route_load_id;  // The route this order is assigned to be loaded
    int route_unload_id;  // The route this order is assigned to be loaded, may be same as route_load_id and viceversa
    int route_load_index;  // The index order in load route
    int route_unload_index;  // The index order in unload route
}

然后我有 Route 类:

class Route{
    int id; // ID of route, this value should be in OrderDocument.route_load/unload_id
    ArrayList<OrderDocument> orders;  // **I WANT TO SORT THIS LIST**
   ...

因此，我有一个函数可以创建 Route 实例并将 OrderDocument 对象添加到其 orders ArrayList 中，因此该列表应该具有 Route.id 位于 中的文档>route_load_id 或在 route_unload_id

中

主要问题

如果路线 id 在 load_id 或 unload_id 中，我需要按加载/卸载索引对这个列表进行排序。 实际上我有以下 Comparator 方法，但不起作用。

private class OrdersComparable implements Comparator<OrderDocument>{
    @Override
    public int compare(OrderDocument x, OrderDocument y) {
        if (x.route_load_id == y.route_load_id)
            return x.route_load_index - y.route_load_index;
        else if (x.route_load_id == y.route_unload_id)
            return x.route_load_index - y.route_unload_index;
        else if (x.route_unload_id == y.route_load_id)
            return x.route_unload_index - y.route_load_index;
        else if (x.route_unload_id == y.route_unload_id)
            return x.route_unload_index - y.route_unload_index;
        else
            return 0;
    }
}

示例

43号公路上有4个订单，2个待装，4个待卸。

OrderDocument('order_id':1, 'route_load_id':43, 'route_unload_id':null, 'route_load_index':0, 'route_unload_index':null)
OrderDocument('order_id':2, 'route_load_id':43, 'route_unload_id':null, 'route_load_index':2, 'route_unload_index':null)
OrderDocument('order_id':3, 'route_load_id':null, 'route_unload_id':43, 'route_load_index':null, 'route_unload_index':1)
OrderDocument('order_id':1, 'route_load_id':null, 'route_unload_id':43, 'route_load_index':null, 'route_unload_index':3)

按 order_id 的实际订单:1, 2, 3, 1

按 order_id 要求的订单:1, 3, 2, 1

Answer 1

如果您使用 null 值(以及可空的相应类型)，您必须检查您的条件是否比较空值，否则将满足不理想的条件:

class OrderDocument implements Comparable<ModelTask> {
    int order_id;  // The document ID
    Integer route_load_id;  // The route this order is assigned to be loaded
    Integer route_unload_id;  // The route this order is assigned to be loaded, may be same as route_load_id and viceversa
    Integer route_load_index;  // The index order in load route
    Integer route_unload_index;  // The index order in unload route
}

class OrdersComparable implements Comparator<OrderDocument> {
@Override
public int compare(OrderDocument x, OrderDocument y) {
    if (x.route_load_id == y.route_load_id && x.route_load_id != null)
        return Integer.compare(x.route_load_index, y.route_load_index);

    if (x.route_load_id == y.route_unload_id && x.route_load_id != null)
        return Integer.compare(x.route_load_index, y.route_unload_index);

    if (x.route_unload_id == y.route_load_id && x.route_unload_id != null)
        return Integer.compare(x.route_unload_index, y.route_load_index);

    if (x.route_unload_id == y.route_unload_id && x.route_unload_id != null)
        return Integer.compare(x.route_unload_index, y.route_unload_index);

    return 0;
}
}