<p>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?</p>

<pre><code>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
</code></pre>

Apache Commons has String diff
org.apache.commons.lang.StringUtils
```
```
StringUtils.difference("foobar", "foo");
```
```