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, Apr 15 '10 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, Apr 15 '10 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, Apr 15 '10 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, Apr 15 '10 at 18:16

score 6 · Accepted Answer · edited Jun 08 '18 at 11:59

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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 08 '18 at 11:59

Robert

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answered Apr 15 '10 at 16:09

danben

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Old question, but link seems to be broken. – Fergus Barker Apr 26 '13 at 04:47
Would love to see whats on the other end of that link! – Troyseph Feb 13 '15 at 15:15
New links have been added. – Robert Jun 08 '18 at 11:59

score 1 · Answer 2 · edited May 23 '17 at 12:30

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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 '17 at 12:30

Community

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answered Apr 15 '10 at 16:42

Bert F

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Ah, I see a StringUtils.difference(str1, str2).length() and StringUtils.difference(str2, str1).length() Should work just fine. Thanks. – Zombies Apr 15 '10 at 17:11

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

2 Answers2