Calendar 计算年龄

//由出生日期获取年龄
public static int getAge(Date birthday){
if (birthday == null) {
return 0;
}
Calendar cal = Calendar.getInstance();

if (cal.before(birthday)) {
return 0;
}
//获取当前的年月日
int yearNow = cal.get(Calendar.YEAR);
int monthNow = cal.get(Calendar.MONTH);
int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);

//获取出生年月日
cal.setTime(birthday);
int yearBirth = cal.get(Calendar.YEAR);
int monthBirth = cal.get(Calendar.MONTH);
int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);

int age = yearNow - yearBirth;

if (monthNow <= monthBirth) {
if (monthNow == monthBirth) {
if (dayOfMonthNow < dayOfMonthBirth)
　　age--;
} else {
　　age--;
}
}
　　return age;
}