如何使用 Guava Multimap 的 replaceValues 方法？

Question

I want to add, remove and replace values in a MultiMap provided by Guava.

I do this currently to add values..

static Multimap<Integer, Float> myMultimap;
 myMultimap = ArrayListMultimap.create();
 myMultimap.put(1, (float)4.3);
 myMultimap.put(2, (float)4.9);
 myMultimap.put(1, (float)4.7);
 myMultimap.put(1, (float)4.5);

Removing values is easier with Guava library.

myMultimap.remove(1,(float)4.7);

But how can I use the replaceValues method?

I mean this

 myMultimap.replaceValues(1, (float)4.3);

Say I wanted to replace value 4.3 with a new value 5.99, how should I do that, the method expects some Iterable function and I am not sure as of how to implement it..

This is the error..

The method replaceValues(Integer, Iterable) in the type Multimap is not applicable for the arguments (int, float)

Answer 1

Multimap.replaceValues takes a collection of values that replaces all of the existing values for the given key. From the JavaDoc it looks like you need to use remove followed by put .

If the map is modifiable, you can get a modifiable view on the collection of values mapped to a single key using get , but the view returned is a plain Collection without an atomic replace method. You can always create your own helper method. Note that this method is not thread-safe.

public static <K,V> boolean replaceValue(Multimap<K,V> map, K key, V oldValue, V newValue) {
    if (map.remove(key, oldValue)) {
        map.put(key, newValue);
        return true;
    }
    return false;
}

Answer 2

public class guava_main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
    
        Multimap map = HashMultimap.create();
    
        map.put("game", 1);
        map.put("game", 2);
    
        map.put("book", 4);
        map.put("book", 3);
    
        Iterable iter = map.get("book");
        map.replaceValues("game", iter);
    
        System.out.println(map);
    }
}

// result : {book=[4, 3], game=[4, 3]}