* Removes unused indexes from disk.
*/
public void cleanUpIndexes() {
SimpleSet knownPaths = new SimpleSet();
IJavaSearchScope scope = BasicSearchEngine.createWorkspaceScope();
PatternSearchJob job = new PatternSearchJob(null, SearchEngine.getDefaultSearchParticipant(), scope, null);
Index[] selectedIndexes = job.getIndexes(null);
for (int i = 0, l = selectedIndexes.length; i < l; i++) {
String path = selectedIndexes[i].getIndexFile().getAbsolutePath();
knownPaths.add(path);
}