Question

I have a method returning a list of String that need to be sorted. However, I’m running into the old String number sorting issue and was wondering if any one could assist with a Comparator implementation or point me in the direction of one.

The list is going to return something list this:

State Lower Legislative District 1
State Lower Legislative District 11
State Lower Legislative District 12
...
State Lower Legislative District 2
...
State Lower Legislative District 100
...
State Upper Legislative District 1
State Upper Legislative District 11
...

So, first I need to do a basic String sort, but then I need to sort by the number. The number to sort on should always trail, and may be 2 or 3 digits.

(Edit) My initial thought is to split the string on space, run StringUtils.isNumeric on the number portion, then sort. However, it seems a bit of a kludge to me.

Can anyone assist?

Answer 1

There is an article about this on Coding Horror. This is called natural sorting, where you effectively treat a group of digits as a single “character”. See this question for some Java implementations of the idea.

Sorting for Humans : Natural Sort Order

The default sort functions in almost every programming language are poorly suited for human consumption. What do I mean by that? Well, consider the difference between sorting filenames in Windows explorer, and sorting those very same filenames via Array.Sort() code:

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