Problem: i have some data in a text file, which contains 2 java.lang.Strings: the first one contains my data value, and the second one is the data type, i.e. “java.lang.Long”, “java.lang.Double”, etc.

How do i construct an object of the appropriate type containing the value in my text file?

Crappy solution: a loooong chain of if-else-if scanning through every supported type for choosing the appropriate parse* (Integer.parseInt, Double.parseDouble, etc.) method.

Why is this so crappy? Simply, because adding a supported type requires extending the if-else-if chain which may easily become too long and unreadable.

Funky solution: use the mighty powers of Java reflection!

Class objClass = Class.forName(type);
Class[] prototype = {String.class};
Constructor ctor = objClass.getConstructor(prototype);
return ctor.newInstance(new Object[]{value});

So what do these 4 lines do?
We get an instance of the Class object representing the class identified by the “type” String (the second string in our data file) and then we get the constructor which takes a single String as parameter, aka the constructor whose prototype is the one identified by our “prototype” variable; finally, we execute the constructor passing the value string.

Why is this so funky?

First of all, because it does in 4 lines of code what was done in a whoooole lot of lines in the crappy solution, but the very funky aspect of this solution is that it works not only with primitive types such as Integer, Long or Double, but also with any type which can be constructed with a String!

Veeeeeeeery funky!