# operator []= method

void operator []= (K key, V value)
override

Associates the `key` with the given `value`.

If the key was already in the map, its associated value is changed. Otherwise the key/value pair is added to the map.

## Implementation

    void operator []=(K key, V value) {
      if (key == null) throw new ArgumentError(key);
      // Splay on the key to move the last node on the search path for
      // the key to the root of the tree.
      int comp = _splay(key);
      if (comp == 0) {
        _root.value = value;
        return;
      }
      _addNewRoot(new _SplayTreeMapNode(key, value), comp);
    }