Java - using Map how to find matching Key when Values are stored a List of strings

Question

All,

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

    Map> cat = new HashMap

        

Answer 1

You need to create the inversed map:

Map fruitCategoryMap = new HashMap<>();
for(Entry> catEntry : cat.entrySet()) {
    for(String fruit : catEntry.getValue()) {
        fruitCategoryMap.put(fruit, catEntry.getKey());
    }
}

Then you can simply do:

String category = fruitCategoryMap.get("Banana"); // "Fruit"