public void follow(File sourceFile, Line sourceLine) {
   Line line = findLineForOccurrence(sourceFile, sourceLine);
   if (line == null) return;
   for (EditorIterator it = new EditorIterator(); it.hasNext(); ) {
     Editor ed = it.next();
     if (ed.getBuffer() == this) {
       ed.moveDotTo(line, 0);
       ed.updateDisplay();
     }
   }
 }
 // Move dot to line (in all editors) and call findOccurrenceAtDot().
 private void findOccurrence(Editor editor, Line line) {
   if (line instanceof OccurrenceLine) {
     for (EditorIterator it = new EditorIterator(); it.hasNext(); ) {
       Editor ed = it.next();
       if (ed.getBuffer() == this) {
         ed.moveDotTo(line, 0);
         ed.updateDisplay();
       }
     }
     findOccurrenceAtDot(editor, false);
   }
 }