将 ArrayList 动态分解为 ArrayList 的 ArrayList

Question

我正在尝试创建一种方法，根据 myObj 类的属性值将对象数组列表分解为多个数组列表。

private static ArrayList<ArrayList<Ticket>> splitList(ArrayList<Ticket> arrayList){
    ArrayList<ArrayList<Ticket>> smallLists = new ArrayList<>();
    for(int i = 0; i < arrayList.size(); i++){
        for(Ticket eachTick: Ticket.getTickets()){
            if(arrayList.get(i).getCategory().equals(eachTick.getCategory())){
                smallLists.add(...);
            }
        }


    }
    return smallLists;
}

如果有更好的方法来做我正在尝试的事情，请告诉我。

Answer 1

您是否尝试为输入列表中找到的每个票证类别创建一个列表？如果是这种情况，那么我同意 Dawood ibn Kareem：使用根据类别查找正确列表的地图。像这样的：

private static ArrayList<ArrayList<Ticket>> splitList(ArrayList<Ticket> inputList) {
    Map<String, ArrayList<Ticket>> map = new HashMap<>();
    // your ticket categories here
    // (array used for simplicity; you should use a Set, and you should also maintain the valid categories inside your Ticket class, not here)
    String[] categories = new String[] {'a', 'b', 'c' };
    for (int i = 0; i < categories.length; i++) {
        map.put(categories[i], new ArrayList<Ticket>());
    }
    for (int i = 0; i < inputList.size(); i++) {
        Ticket t = inputList.get(i);
        map.get(t.getCategory()).add(t);
    }
    // Convert to list of lists
    return new ArrayList<>(map.values());
}