Java - 使用Map如何在存储值时找到匹配的键字符串列表 [英] Java - using Map how to find matching Key when Values are stored a List of strings

问题描述

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我有一个类别和子类别的地图，如下所示：

I have a map with categories and subcategories as lists like this:

    Map<String,List<String>> cat = new HashMap<String,List<String>>();

    List<String> fruit = new ArrayList<String>();
    fruit.add("Apple");
    fruit.add("Pear");
    fruit.add("Banana");

    cat.put("Fruits", fruit);

    List<String> vegetable = new ArrayList<String>();
    vegetable.add("Carrot");
    vegetable.add("Leak");
    vegetable.add("Parsnip");

    cat.put("Vegetables", vegetable);

我想查找胡萝卜是否在地图中，哪个键（水果）它匹配，但是：

I want to find if "Carrot" is in the map and to which key ("Fruit') it matches, however:

    if (cat.containsValue("Carrot")) {System.out.println("Cat contains Leak");}

将False作为结果，如何匹配胡萝卜键值蔬菜

gives False as outcome. How can I match "Carrot" and get back the key value "Vegetable"

Thx。

推荐答案

钥匙，并检查值，如果发现，然后打破循环。

Iterate thought all the keys and check in the value if found then break the loop.

for (String key : cat.keySet()) {
    if (cat.get(key).contains("Carrot")) {
        System.out.println(key + " contains Carrot");
        break;
    }
}

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