如何將以下數據轉換為LOOP

Question

我正在嘗試將以下內容轉換成循環，但是我白費力氣了，我希望有人幫助我將這種類型的數據轉換成循環。

ArrayList<String> parentList = new ArrayList<>();
        ArrayList<ArrayList> childListHolder = new ArrayList<>();

        parentList.add("Parent1");
        parentList.add("Parent2");
        parentList.add("Parent3");

        ArrayList<String> childNameList = new ArrayList<>();
        childNameList.add("Child1");
        childNameList.add("Child2");
        childNameList.add("Child3");

        childListHolder.add(childNameList);

        childNameList = new ArrayList<>();
        childNameList.add("Child4");
        childNameList.add("Child5");
        childNameList.add("Child6");

        childListHolder.add(childNameList);

        childNameList = new ArrayList<>();
        childNameList.add("Child7");
        childNameList.add("Child8");
        childNameList.add("Child9");

        childListHolder.add(childNameList);

Answer 1

這里不需要循環，也不ArrayList用作原始類型，而希望使用List接口。 使用Arrays.asList(T...)生成您的List 。 喜歡，

List<List<String>> childListHolder = new ArrayList<>();
List<String> parentList = Arrays.asList("Fruits & Vegetables", 
        "Beverages & Health", "Home & Kitchen");
childListHolder.add(Arrays.asList("Apple", "Mango", "Banana"));
childListHolder.add(Arrays.asList("Red bull", "Maa", "Horlicks"));
childListHolder.add(Arrays.asList("Knife", "Vessels", "Spoons"));

Answer 2

與循環代碼等效的是：

ArrayList<String> parentList = new ArrayList<>();
ArrayList<ArrayList> childListHolder = new ArrayList<>();

for (int i = 1; i <= 3; i++) {
    parentList.add("Parent" + i);

    ArrayList<String> childNameList = new ArrayList<>();
    for (int j = 1; j <= 3; j++) {
        childNameList.add("Child" + (3 * (i - 1) + j));
    }
    childListHolder.add(childNameList);
}