如何在Java中执行字符串差异？

我需要在Java字符串之间执行差异。我希望能够使用原始字符串和差异版本重建字符串。有人用Java做过吗？你使用什么库？

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