code: public synchronized boolean add(E e) {
          modCount++;
          ensureCapacityHelper(elementCount + 1);
          elementData[elementCount++] = e;
          return true;
      }
docs: Appends the specified element to the end of this Vector.
  
  @param e element to be appended to this Vector
  @return {@code true} (as specified by {@link Collection#add})
  @since 1.2