How to perform string Diffs in Java?

user_2138 0
Viewed 81736

I need to perform Diffs between Java strings. I would like to be able to rebuild a string using the original string and diff versions. Has anyone done this in Java? What library do you use?

String a1; // This can be a long text
String a2; // ej. above text with spelling corrections
String a3; // ej. above text with spelling corrections and an additional sentence

Diff diff = new Diff();
String differences_a1_a2 = Diff.getDifferences(a,changed_a);
String differences_a2_a3 = Diff.getDifferences(a,changed_a);    
String[] diffs = new String[]{a,differences_a1_a2,differences_a2_a3};
String new_a3 = Diff.build(diffs);
a3.equals(new_a3); // this is true
diff java
8 Answers
user_215480

Apache Commons has String diff

org.apache.commons.lang.StringUtils

StringUtils.difference("foobar", "foo");
Paul_Whelan_30500
user_756090

As Torsten Says you can use

org.apache.commons.lang.StringUtils;

System.err.println(StringUtils.getLevenshteinDistance("foobar", "bar"));
Paul_Whelan_30500

If you need to deal with differences between big amounts of data and have the differences efficiently compressed, you could try a Java implementation of xdelta, which in turn implements RFC 3284 (VCDIFF) for binary diffs (should work with strings too).

Alexander_167240

Use the Levenshtein distance and extract the edit logs from the matrix the algorithm builds up. The Wikipedia article links to a couple of implementations, I'm sure there's a Java implementation among in.

Levenshtein is a special case of the Longest Common Subsequence algorithm, you might also want to have a look at that.

user_95670

Apache Commons Text now has StringsComparator:

StringsComparator c = new StringsComparator(s1, s2);
c.getScript().visit(new CommandVisitor<Character>() {

    @Override
    public void visitKeepCommand(Character object) {
        System.out.println("k: " + object);
    }

    @Override
    public void visitInsertCommand(Character object) {
        System.out.println("i: " + object);
    }

    @Override
    public void visitDeleteCommand(Character object) {
        System.out.println("d: " + object);
    }
});
user_1842010
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