/**
* Creates a new <code>Years</code> by parsing a string in the ISO8601 format 'PnY'.
*
* <p>The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the years
* component may be non-zero. If any other component is non-zero, an exception will be thrown.
*
* @param periodStr the period string, null returns zero
* @return the period in years
* @throws IllegalArgumentException if the string format is invalid
*/
public static Years parseYears(String periodStr) {
if (periodStr == null) {
return Years.ZERO;
}
Period p = PARSER.parsePeriod(periodStr);
return Years.years(p.getYears());
}
