birthdayがStringで「1980/01/01」フォーマットだったときパターン
import org.joda.time.LocalDate;
import org.joda.time.Years;
import org.joda.time.format.DateTimeFormat;
public int getAge() {
LocalDate now = new LocalDate();
LocalDate birthday = LocalDate.parse(getBirthday(), DateTimeFormat.forPattern("yyyy/MM/dd"));
Years age = Years.yearsBetween(birthday, now);
return age.getYears();
}