Class that reads data from Excel
You do have to be careful when calling methods from the constructor though. See the answer to the same question here.
But as long as you don't call overridable methods (and don't pass a reference to this) there is no problem.

The biggest issue I have with your method is the naming. By convention a method starting with getXXX() implies that it actually returns that XXX. If you would rename your method to something like initFromExcelData() for example it would be a lot clearer what the method does.

I personally would also do the assignments for first and last name inside this method. Especially if these are the only things you want to do with the excel. That way you can make the map local to that init method.