/**
  * Debugging routine only. Returns non-null JNIHandleBlock containing the JNI handle or null if
  * this handle block and its successors did not contain it (or if the handle was deleted).
  */
 public JNIHandleBlock blockContainingHandle(Address jniHandle) {
   JNIHandleBlock cur = this;
   while (cur != null) {
     if (indexOfHandle(jniHandle) >= 0) {
       return cur;
     }
     cur = cur.next();
   }
   return null;
 }