description

# lastKeyBefore method Null safety

K? lastKeyBefore (

1. K key

)

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

## Implementation

    K? lastKeyBefore(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!.left;
      if (node == null) return null;
      var nodeRight = node.right;
      while (nodeRight != null) {
        node = nodeRight;
        nodeRight = node.right;
      }
      return node!.key;
    }