description

# firstKeyAfter method Null safety

K? firstKeyAfter (

1. K key

)

Get the first key in the map that is strictly larger than `key`. Returns `null` if no key was not found.

## Implementation

    K? firstKeyAfter(K key) {
      if (key == null) throw ArgumentError(key);
      if (_root == null) return null;
      int comp = _splay(key);
      if (comp > 0) return _root!.key;
      _SplayTreeMapNode<K, V>? node = _root!.right;
      if (node == null) return null;
      var nodeLeft = node.left;
      while (nodeLeft != null) {
        node = nodeLeft;
        nodeLeft = node.left;
      }
      return node!.key;
    }