code: public int getInt(final String propertyName) {
          if (propertyName == null) {
              throw new NullPointerException("propertyName must not be null.");
          }
          Integer index = propertyMap.get(propertyName);
          if (index == null) {
              throw new IllegalArgumentException("non existent property: '"
                      + propertyName + "'.");
          }
          if (data[index].length == 0) {
              throw new IndexOutOfBoundsException(
                      "The property value is a list with zero entries.");
          }
          return (int) data[index][0];
      }
docs: Gets a property value of this element.
  <p>If the property is a list-property, the first element is returned.</p>
  @param propertyName Name of the property.
  @return Value of the current element casted to {@code int}.
  @throws NullPointerException if {@code propertyName} is {@code null}.
  @throws IllegalArgumentException if the element type does not have
  a property with the given name.
  @throws IndexOutOfBoundsException if the requested property is a
  list property with zero elements.