public Period plusYears(long yearsToAdd){
  if (yearsToAdd == 0) {
    return this;
  }
  return create(Math.toIntExact(Math.addExact(years,yearsToAdd)),months,days);
}

public Period plusYears ( long yearsToAdd ) { if ( yearsToAdd == 0 ) { return this ; } return create ( Math . toIntExact ( Math . addExact ( years , yearsToAdd ) ) , months , days ) ; }
returns a copy of this period with the specified years added . < p > this adds the amount to the years unit in a copy of this period . the months and days units are unaffected . for example , " 1 year , 6 months and 3 days " plus 2 years returns " 3 years , 6 months and 3 days " . < p > this instance is immutable and unaffected by this method call .
