The point is to parse the input into a structure which always upholds the predicates you care about so you don't end up continuously defensively programming in ifs and asserts.
In Java, you'd implement this by making a class with a private constructor, no mutator methods, and a static factory method that throws an exception if the parsing fails. Since the only way to get an instance of the class is through the factory method, you've made illegal states unrepresentable and know that the class always holds to its invariants. No methods on instances of that class will throw exceptions from then on, so you've successfully applied "Parse, Don't Validate" without needing sum types.
The point of the article isn't the particular implementation in Haskell, it's the concept of pushing all data error states to the boundaries of your code, which applies anywhere as long as you translate it into the idioms of your language.