public void addItem(@Nonnull final ExpressionItem item) {
    if (item == null) {
      throw new PreprocessorException("[Expression]Item is null", this.sources, this.includeStack, null);
    }

    if (last.isEmptySlot()) {
      last = new ExpressionTreeElement(item, this.includeStack, this.sources);
    } else {
      last = last.addTreeElement(new ExpressionTreeElement(item, this.includeStack, this.sources));
    }
  }
public void addItem ( @ Nonnull final ExpressionItem item ) { if ( item == null ) { throw new PreprocessorException ( "[Expression]Item is null" , this . sources , this . includeStack , null ) ; } if ( last . isEmptySlot ( ) ) { last = new ExpressionTreeElement ( item , this . includeStack , this . sources ) ; } else { last = last . addTreeElement ( new ExpressionTreeElement ( item , this . includeStack , this . sources ) ) ; } }
Add new expression item into tree

@param item an item to be added, must not be null