JAVA: How to search a map?

问题:

I have a Map that has Strings for its keys and sets (that contain integers) for its values

Say my keys look like this "apple", "banana", "orange", etc.

The user enters text and I save it as a String variable. How do I search my map for an identical key? So if the user types in "apple" how do I give that String to a method and have the method search my map for the "apple" key and return the set of Integers associated with it (values)?

Thanks

回答1:

Use the get method

 Set<Integer> values = map.get("apple");

回答2:

You don't really search a Map, you retrieve values from it thus:

public static void main(String[] args) {
    final Map<String, Set<Integer>> myMap = new HashMap<>();
    //put new values into map
    myMap.put("MyString", new HashSet<Integer>());
    //get Set from Map
    final Set<Integer> mySet = myMap.get("myString");
}

回答3:

return the set of Integers associated with it (values)?

A map requires the keys to be different, hence I assume that your map declaration would look like Map<String, List<Integer>> myMap

To check if a key exists in a Map: myMap.containsKey(key) e.g. myMap.containsKey("apple")

To get the values associated with the key: myMap.get(key) e.g. myMap.get("apple")