Java: String compare library that returns diff count as an int?

Question

Does a library or even standard API call exist that allows me to diff two strings and get the number of diff chars as an int? I wouldn't mind other features, just as long as I can get a more programmatic diff result (such as an int) instead of something that just outputs the entire human readable diff.

Hmmm, how would you decide if characters are different? e.g. if two strings are different lengths would the characters of the longer string count as different characters or the same? Is the order of the characters important? — Tarski
– Tarski, Commented Apr 15, 2010 at 16:01
and what about comparing "steves car" with "steve's car". would that be 1 character different (just the "'") or 6 characters different (the whole "'s car")? i think there are several different ways of specifying this problem. — Kip
– Kip, Commented Apr 15, 2010 at 16:03
Do you need the exact number of different characters? compareTo does something similar but in a lexicographic order and returns an int. — Searles
– Searles, Commented Apr 15, 2010 at 16:09
@tarski: If the strings are longer I want to know about it. Order can be realigned, much like in beyond and compare. @kip: In that example, just 1 char different... so the int returned would be 1. — Zombies
– Zombies, Commented Apr 15, 2010 at 18:16

Robert · Accepted Answer · 2018-06-08 11:59:19Z

6

I think what you want is the Leveshtein distance - this tells you how many changes (insertions, deletions or replacements) are required to transform one string to another.

For example, the difference between abcde and abcdef is 1, because you insert f after the last position in abcde to get abcdef.

The difference between abcde and abcdf is also 1, since you replace e in the first string with f to get the second.

The difference between abcde and abde is 1 because you delete c in the first string to get the second.

A very good implementation can be found in Apache Commons Text: LevenshteinDistance.

Here are some sample implementation in Java.

edited Jun 8, 2018 at 11:59

Robert

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answered Apr 15, 2010 at 16:09

danben

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3 Comments

Fergus Barker Over a year ago

Old question, but link seems to be broken.

Troyseph Over a year ago

Would love to see whats on the other end of that link!

Robert Over a year ago

New links have been added.

Community · Accepted Answer · 2017-05-23 12:30:46Z

1

I don't know of any standard API calls, but you could see this question for references to third-party libraries (not surprising - Google, Apache Commons ...)

How to perform string Diffs in Java?
How to perform string Diffs in Java?

edited May 23, 2017 at 12:30

CommunityBot

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answered Apr 15, 2010 at 16:42

Bert F

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1 Comment

Zombies Over a year ago

Ah, I see a StringUtils.difference(str1, str2).length() and StringUtils.difference(str2, str1).length() Should work just fine. Thanks.

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