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年龄就是把当前的年份与用户的年份相减得到一个对象值1。然后将用户输入日期中的年份换成当年的，组成一个新的日期，将这新的日期与当天的日期进行比较，得到另一个对象值2。这个对象值2就是距离用户的生日的天数。这天数是正，那对象值1就是用户的年龄，是负把对象值+1就好。参考两日期之间的天数差方法：
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public static int getDiffDay(String firstString, String secondString) {
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Date firstDate = null;
Date secondDate = null;
try {
firstDate = df.parse(firstString);
secondDate = df.parse(secondString);
} catch (Exception e) {
// 日期型字符串格式错误
}
int nDay = (int) ((secondDate.getTime() - firstDate.getTime()) / (24 * 60 * 60 * 1000));
return nDay;
}
这是一段javascript写的，无论是java或javascript原理都一样，进攻参考
!-- Begin
function run() {
with (document.agecalc) {
dd = parseInt(day.selectedIndex) + 1;
mm = parseInt(month.selectedIndex) + 1;
yy = year.value;
if (yy.length != 4 || isNaN(yy)) {
document.agecalc.timealive.value = "请输入4位数的年份.";
document.agecalc.year.select();
document.agecalc.year.focus();
return;
}
}
days = new Date();
gdate = days.getDate();
gmonth = days.getMonth();
gyear = days.getYear();
if (gyear 2000) gyear += 1900;
age = gyear - yy;
if ((mm == (gmonth + 1)) (dd = parseInt(gdate))) {
age = age;
} else {
if (mm = (gmonth)) {
age = age;
} else {
age = age - 1;
}
}
if (age == 0)
age = age;
document.agecalc.timealive.value = "你已经满了 " + age+ " 周岁 . . .\n\n";
if (mm = (gmonth + 1))
age = age - 1;
if ((mm == (gmonth + 1)) (dd parseInt(gdate)))
age = age + 1;
var m;
var n;
if (mm == 12) n = 31 - dd;
if (mm == 11) n = 61 - dd;
if (mm == 10) n = 92 - dd;
if (mm == 9) n = 122 - dd;
if (mm == 8) n = 153 - dd;
if (mm == 7) n = 184 - dd;
if (mm == 6) n = 214 - dd;
if (mm == 5) n = 245 - dd;
if (mm == 4) n = 275 - dd;
if (mm == 3) n = 306 - dd;
if (mm == 2) { n = 334 - dd; if (leapyear(yy)) n++; }
if (mm == 1) { n = 365 - dd; if (leapyear(yy)) n++; }
if (gmonth == 1) m = 31;
if (gmonth == 2) {
m = 59;
if (leapyear(gyear)) m++;
}
if (gmonth == 3) { m = 90; if (leapyear(gyear)) m++; }
if (gmonth == 4) { m = 120; if (leapyear(gyear)) m++; }
if (gmonth == 5) { m = 151; if (leapyear(gyear)) m++; }
if (gmonth == 6) { m = 181; if (leapyear(gyear)) m++; }
if (gmonth == 7) { m = 212; if (leapyear(gyear)) m++; }
if (gmonth == 8) { m = 243; if (leapyear(gyear)) m++; }
if (gmonth == 9) { m = 273; if (leapyear(gyear)) m++; }
if (gmonth == 10) { m = 304; if (leapyear(gyear)) m++; }
if (gmonth == 11) { m = 334; if (leapyear(gyear)) m++; }
if (gmonth == 12) { m = 365; if (leapyear(gyear)) m++; }
months = age * 12;
months += 12 - parseInt(mm);
months += gmonth;
totdays = (parseInt(age) * 365);
totdays += age / 4;
totdays = parseInt(totdays) + gdate + m + n;
if (gmonth == 1) p = 31 + gdate;
if (gmonth == 2) {
p = 59 + gdate;
if (leapyear(gyear)) m = m+1;
}
if (gmonth == 3) { p = 90 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 4) { p = 120 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 5) { p = 151 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 6) { p = 181 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 7) { p = 212 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 8) { p = 243 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 9) { p = 273 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 10) { p = 304 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 11) { p = 334 + gdate; if (leapyear(gyear)) p++; }
if (gmonth == 12) { p = 365 + gdate; if (leapyear(gyear)) p++; }
weeks = (age * 365) + n + p;
weeks = weeks / 7;
etcdays = parseFloat(weeks) - parseInt(weeks);
etcdays = Math.round(etcdays * 7);
weeks = parseInt(weeks);
etcdays += parseInt(age / 4);
if (etcdays 7)
weeks += parseInt(etcdays / 7);
document.agecalc.timealive.value += " 或 " + months + " 月龄\n";
document.agecalc.timealive.value += " 或 " + weeks + " 周龄\n";
document.agecalc.timealive.value += " 或 " + totdays + " 日龄\n";
var time = new Date();
ghour = time.getHours();
gmin = time.getMinutes();
gsec = time.getSeconds();
hour = ((age * 365) + n + p) * 24;
hour += (parseInt(age / 4) * 24);
document.agecalc.timealive.value += " 或 " + hour + " 小时\n";
var min = (hour * 60) + gmin;
document.agecalc.timealive.value += " 或 " + min + " 分钟\n";
sec = (min * 60) + gsec;
document.agecalc.timealive.value += " 或 " + sec + " 秒钟";
mm = mm - 1;
var r;
if (mm == 0) r = 0;
if (mm == 1) r = 31;
if (mm == 2) { r = 59; if (leapyear(gyear)) m++; }
if (mm == 3) { r = 90; if (leapyear(gyear)) r++; }
if (mm == 4) { r = 120; if (leapyear(gyear)) r++; }
if (mm == 5) { r = 151; if (leapyear(gyear)) r++; }
if (mm == 6) { r = 181; if (leapyear(gyear)) r++; }
if (mm == 7) { r = 212; if (leapyear(gyear)) r++; }
if (mm == 8) { r = 243; if (leapyear(gyear)) r++; }
if (mm == 9) { r = 273; if (leapyear(gyear)) r++; }
if (mm == 10) { r = 304; if (leapyear(gyear)) r++; }
if (mm == 11) { r = 334; if (leapyear(gyear)) r++; }
mm = mm + 1;
r = parseInt(r) + parseInt(dd);
if ((mm = (gmonth + 1)) (dd gdate)) {
bday = r - m - gdate;
}
else {
if ((leapyear(gyear)) ((mm 2) (dd 29))) {
a = 366;
} else {
a = 365;
}
bday = a + (r - m - gdate);
}
nhour = 24 - parseInt(ghour);
nmin = 60 - parseInt(gmin);
nsec = 60 - parseInt(gsec);
while (bday 366) bday -= 365;
if (((bday == 366) (leapyear(gyear)) || ((bday == 365) (!leapyear(gyear))))) {
document.agecalc.timealive.value += "\n\nSenlon祝贺您！今天是你的生日！祝你生日快乐！";
} else {
document.agecalc.timealive.value += "\n\n另外，你下一个生日距今还有：\n"
+ bday + " 天 " + nhour + " 小时 " + nmin + " 分 " + nsec + " 秒";
setTimeout("run()", 1000);
}
}
function leapyear(a) {
if (((a%4 == 0) (a%100 != 0)) || (a%400 == 0))
return true;
else
return false;
}
// End --
来自
import java.util.Calendar;
import java.util.Date;
import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
public class H {
public static void main(String args[]) {
new Time("年龄计算器");
}
}
class Time extends Frame implements ActionListener {
Calendar calendar;
Button button;
TextField t1, t2, t3;
Label l, l1, l2, l3;
Time(String s) {
super(s);
setLayout(new FlowLayout());
button = new Button("确定");
button.addActionListener(this);
t1 = new TextField(2);
t2 = new TextField(2);
t3 = new TextField(2);
l = new Label(" 请输入您的生日 ");
l.setBackground(Color.cyan);
l1 = new Label("年");
l2 = new Label("月");
l3 = new Label("日");
add(l);
add(t1);
add(l1);
add(t2);
add(l2);
add(t3);
add(l3);
add(button);
setBounds(100, 100, 280, 100);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
setVisible(true);
validate();
}
public void actionPerformed(ActionEvent e) {
calendar = Calendar.getInstance();
calendar.setTime(new Date());
NumberFormat f = NumberFormat.getInstance();
long time = calendar.getTimeInMillis();
if (e.getSource() == button) {
try {
int n = Integer.parseInt(t1.getText());
int y = Integer.parseInt(t2.getText());
int r = Integer.parseInt(t3.getText());
calendar.set(n, y - 1, r);
double time1 = calendar.getTimeInMillis();
double c = (time - time1) / (1000 * 60 * 60 * 24);
double d = c/365;
f.setMaximumFractionDigits(2);
String s = f.format(d);
l.setText("您的年龄约为" + s + " 岁");
} catch (NumberFormatException ee) {
l.setText("请正确输入");
}
}
}
}
功底浅薄，如果有问题，还望指教。
计算全班同学年龄之和。
思路：从键盘上依次输入每个同学的年龄，然后求和输出：
import java.util.Scanner;
public class TestMain {
public static void main(String[] args) {
int sum=0;
Scanner in =new Scanner(System.in);
int n = in.nextInt();
sum+=n；
System.out.println(sum);
}
}
实现步骤：
1、获取当前时间
2、判断出生日期是否小于当前时间，如果大于，则引发一场
3、从当前时间中取出年、月、日；从出生日期中取出年、月、日，年份相减
4、然后做具体判断
示例代码如下：
public static int getAge(Date birthDay) throws Exception {
//获取当前系统时间
Calendar cal = Calendar.getInstance();
//如果出生日期大于当前时间，则抛出异常
if (cal.before(birthDay)) {
throw new IllegalArgumentException(
"The birthDay is before Now.It's unbelievable!");
}
//取出系统当前时间的年、月、日部分
int yearNow = cal.get(Calendar.YEAR);
int monthNow = cal.get(Calendar.MONTH);
int dayOfMonthNow = cal.get(Calendar.DAY_OF_MONTH);
//将日期设置为出生日期
cal.setTime(birthDay);
//取出出生日期的年、月、日部分
int yearBirth = cal.get(Calendar.YEAR);
int monthBirth = cal.get(Calendar.MONTH);
int dayOfMonthBirth = cal.get(Calendar.DAY_OF_MONTH);
//当前年份与出生年份相减，初步计算年龄
int age = yearNow - yearBirth;
//当前月份与出生日期的月份相比，如果月份小于出生月份，则年龄上减1，表示不满多少周岁
if (monthNow = monthBirth) {
//如果月份相等，在比较日期，如果当前日，小于出生日，也减1，表示不满多少周岁
if (monthNow == monthBirth) {
if (dayOfMonthNow dayOfMonthBirth) age--;
}else{
age--;
}
}
System.out.println("age:"+age);
return age;
}
刚写出来，其实就是字符串的截取。
package com.swing;
import java.util.Calendar;
import java.util.Timer;
public class NianLing {
public static void main(String[] args) {
String s = "610400199011100000";
s = s.substring(6, s.length()-8);
System.out.println(s);
Calendar cal = Calendar.getInstance();
java.util.Date date = cal.getTime();
String s1 = date.toString();
String s2 = (String) s1.subSequence(s1.length()-4, s1.length());
System.out.println(date);
System.out.println(s2);
Integer int1 = Integer.parseInt(s);
Integer int2 = Integer.parseInt(s2);
Integer age = int2-int1;
System.out.println("age : " + age);
}
}
输出结果：age：22
1990
Fri Dec 14 23:26:52 CST 2012
2012
age : 22