src/jdk.compiler/share/classes/com/sun/source/util/TreeScanner.java

*** 73,82 ****
--- 73,86 ----
   * @author Peter von der Ahé
   * @author Jonathan Gibbons
   * @since 1.6
   */
  public class TreeScanner<R,P> implements TreeVisitor<R,P> {
+     /**
+      * Constructor for subclasses to call.
+      */
+     public TreeScanner() {}
  
      /**
       * Scans a single node.
       * @param tree the node to be scanned
       * @param p a parameter value passed to the visit method