putIfAbsent method
Throws an UnsupportedError; operations that change the map are disallowed.
Implementation
@override
V putIfAbsent(K key, V Function() ifAbsent) => _throw();
Throws an UnsupportedError; operations that change the map are disallowed.
@override
V putIfAbsent(K key, V Function() ifAbsent) => _throw();