If you use Guava (v11 minimum) in your project you can use Maps::transformValues.
Map<String, Column> newColumnMap = Maps.transformValues(
originalColumnMap,
Column::new // equivalent to: x -> new Column(x)
)
Note: The values of this map are evaluated lazily. If the transformation is expensive you can copy the result to a new map like suggested in the Guava docs.
To avoid lazy evaluation when the returned map doesn't need to be a view, copy the returned map into a new map of your choosing.