How to update a value in a map if it exists else insert it

Question

I did a search and was amazed this hadn't been asked before (at least I couldn't find it).

I have a map like this:

Map<String, String> myMap

I know that I can check if a key exists within the map usingcontainsKey(Object key); and I can replace a value using replace(String key, String value); and naturally put a value using put(String key, String value);

Now if I want to check a value if it exists update it, else insert it, I have to use a condition:

if(myMap.containsKey(key)) {
    myMap.replace(key, value);
} else {
    myMap.put(key, value);
}

Is there a better way of doing this? I personally feel the condition is a bit unnecessary and overcomplicating something which could be one line rather than five!

Answer 1

The replace will be done by put():

From the documentation of HashMap

public V put(K key, V value) Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

So you only need

myMap.put(key, value);

Answer 2

Remove all the code and below line is enough.

myMap.put(key, value);

That already checks and replaces if any value exist already.

Answer 3

You can just use the #put() method, it will replace the existing item if there is one. By the way AbstractMap (the superclass of HashMap) implements #replace() this way:

default boolean replace(K key, V oldValue, V newValue) {
     Object curValue = get(key);
     if (!Objects.equals(curValue, oldValue) ||
         (curValue == null && !containsKey(key))) {
         return false;
     }
     put(key, newValue);
     return true;
 }

In your case, you don't need the extra checks of this method.