JAVA计算日期相差的天数、年差，获取当前月份等
示例代码：
public static void main(String[] args) {
//日期格式化
DateUtil.dateToString(new Date(), "yyyy-MM-dd");
//两个日期的相差天数
long day = DateUtil.dayDiff(DateUtil.stringtoDate("2017-06-22", "yyyy-MM-dd"),
DateUtil.stringtoDate(settlementDate, "yyyy-MM-dd"));
}
工具类：
import java.text.DateFormat;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.regex.Pattern;
public class DateUtil {
// 格式：年－月－日 小时：分钟：秒
public static final String FORMAT_ONE = "yyyy-MM-dd HH:mm:ss";
// 格式：年－月－日 小时：分钟
public static final String FORMAT_TWO = "yyyy-MM-dd HH:mm";
// 格式：年月日 小时分钟秒
public static final String FORMAT_THREE = "yyyyMMdd-HHmmss";
// 格式：年月日
public static final String FORMAT_FOUR = "yyyyMMdd";
// 格式：年－月－日
public static final String LONG_DATE_FORMAT = "yyyy-MM-dd";
// 格式：月－日
public static final String SHORT_DATE_FORMAT = "MM-dd";
// 格式：小时：分钟：秒
public static final String LONG_TIME_FORMAT = "HH:mm:ss";
// 格式：年-月
public static final String MONTG_DATE_FORMAT = "yyyy-MM";
// 年的加减
public static final int SUB_YEAR = Calendar.YEAR;
// 月加减
public static final int SUB_MONTH = Calendar.MONTH;
// 天的加减
public static final int SUB_DAY = Calendar.DATE;
// 小时的加减
public static final int SUB_HOUR = Calendar.HOUR;
// 分钟的加减
public static final int SUB_MINUTE = Calendar.MINUTE;
// 秒的加减
public static final int SUB_SECOND = Calendar.SECOND;
static final String dayNames[] = {
"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
public DateUtil() {
}
/**
* 把符合日期格式的字符串转换为日期类型
*/
public static Date stringtoDate(String dateStr, String format) {
Date d = null;
SimpleDateFormat formater = new SimpleDateFormat(format);
try {
formater.setLenient(false);
d = formater.parse(dateStr);
} catch (Exception e) {
// log.error(e);
d = null;
}
return d;
}
/**
* 把符合日期格式的字符串转换为日期类型
*/
public static Date stringtoDate(String dateStr, String format, ParsePosition pos) {
Date d = null;
SimpleDateFormat formater = new SimpleDateFormat(format);
try {
formater.setLenient(false);
d = formater.parse(dateStr, pos);
} catch (Exception e) {
d = null;
}
return d;
}
/**
* 把日期转换为字符串
*/
public static String dateToString(Date date, String format) {
String result = "";
SimpleDateFormat formater = new SimpleDateFormat(format);
try {
result = formater.format(date);
} catch (Exception e) {
// log.error(e);
}
return result;
}
/**
* 获取当前时间的指定格式
*/
public static String getCurrDate(String format) {
return dateToString(new Date(), format);
}
/**
* 得到指定日期前(后)的日期
*/
public static String dateSub(int dateKind, String dateStr, int amount) {
Date date = stringtoDate(dateStr, MONTG_DATE_FORMAT);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(dateKind, amount);
return dateToString(calendar.getTime(), FORMAT_ONE);
}
/**
* 昨日日期
*/
public static String yearthDate(String dateStr) {
Date date = stringtoDate(dateStr, LONG_DATE_FORMAT);// 取时间
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(calendar.DATE, -1);// 把日期往后增加一天.整数往后推,负数往前移动
// date=calendar.getTime(); //这个时间就是日期往后推一天的结果
return dateToString(calendar.getTime(), LONG_DATE_FORMAT);
}
/**
* 两个日期相减
*/
public static long timeSub(String firstTime, String secTime) {
long first = stringtoDate(firstTime, FORMAT_ONE).getTime();
long second = stringtoDate(secTime, FORMAT_ONE).getTime();
return (second - first) / 1000;
}
/**
* 两个日期相减 参数地DATE second 两个日期相差的秒
*/
public static boolean timeSub(Date firstTime, Date secTime, long secs) {
long first = firstTime.getTime();
long second = secTime.getTime();
// 判断两个时间 是否间隔那么长 secs。
return (second - first - secs) > 0 ? false : true;
}
/**
* 两个日期相减 参数地DATE
*/
public static boolean timeSub(Date firstTime, Date secTime) {
long first = firstTime.getTime();
long second = secTime.getTime();
return (second - first) > 0 ? false : true;
}
/**
* 获得某月的天数
*/
public static int getDaysOfMonth(String year, String month) {
int days = 0;
if (month.equals("1") || month.equals("3") || month.equals("5") || month.equals("7") || month.equals("8")
|| month.equals("10") || month.equals("12")) {
days = 31;
} else if (month.equals("4") || month.equals("6") || month.equals("9") || month.equals("11")) {
days = 30;
} else {
if ((Integer.parseInt(year) % 4 == 0 && Integer.parseInt(year) % 100 != 0)
|| Integer.parseInt(year) % 400 == 0) {
days = 29;
} else {
days = 28;
}
}
return days;
}
/**
* 获取某年某月的天数
*/
public static int getDaysOfMonth(int year, int month) {
Calendar calendar = Calendar.getInstance();
calendar.set(year, month - 1, 1);
return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
}
/**
* 获得当前日期
*/
public static int getToday() {
Calendar calendar = Calendar.getInstance();
return calendar.get(Calendar.DATE);
}
/**
* 获得当前月份
*/
public static int getToMonth() {
Calendar calendar = Calendar.getInstance();
return calendar.get(Calendar.MONTH) + 1;
}
/**
* 获得当前年份
*/
public static int getToYear() {
Calendar calendar = Calendar.getInstance();
return calendar.get(Calendar.YEAR);
}
/**
* 返回日期的天
*/
public static int getDay(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
return calendar.get(Calendar.DATE);
}
/**
* 返回日期的年
*/
public static int getYear(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
return calendar.get(Calendar.YEAR);
}
/**
* 返回日期的月份，1-12
*/
public static int getMonth(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
return calendar.get(Calendar.MONTH) + 1;
}
/**
* 计算两个日期相差的天数，如果date2 > date1 返回正数，否则返回负数
*/
public static long dayDiff(Date date1, Date date2) {
return (date2.getTime() - date1.getTime()) / 86400000;
}
/**
* 比较两个日期的年差
*/
public static int yearDiff(String before, String after) {
Date beforeDay = stringtoDate(before, LONG_DATE_FORMAT);
Date afterDay = stringtoDate(after, LONG_DATE_FORMAT);
return getYear(afterDay) - getYear(beforeDay);
}
/**
* 比较指定日期与当前日期的差
*/
public static int yearDiffCurr(String after) {
Date beforeDay = new Date();
Date afterDay = stringtoDate(after, LONG_DATE_FORMAT);
return getYear(beforeDay) - getYear(afterDay);
}
/**
* 获取每月的第一周
*/
public static int getFirstWeekdayOfMonth(int year, int month) {
Calendar c = Calendar.getInstance();
c.setFirstDayOfWeek(Calendar.SATURDAY); // 星期天为第一天
c.set(year, month - 1, 1);
return c.get(Calendar.DAY_OF_WEEK);
}
/**
* 获取每月的最后一周
*/
public static int getLastWeekdayOfMonth(int year, int month) {
Calendar c = Calendar.getInstance();
c.setFirstDayOfWeek(Calendar.SATURDAY); // 星期天为第一天
c.set(year, month - 1, getDaysOfMonth(year, month));
return c.get(Calendar.DAY_OF_WEEK);
}
/**
* 获得当前日期字符串，格式"yyyy-MM-dd HH:mm:ss"
*
* @return
*/
public static String getNow() {
Calendar today = Calendar.getInstance();
return dateToString(today.getTime(), FORMAT_ONE);
}
/**
* 判断日期是否有效,包括闰年的情况
*
* @param date
* YYYY-mm-dd
* @return
*/
public static boolean isDate(String date) {
StringBuffer reg = new StringBuffer("^((\\d{2}(([02468][048])|([13579][26]))-?((((0?");
reg.append("[13578])|(1[02]))-?((0?[1-9])|([1-2][0-9])|(3[01])))");
reg.append("|(((0?[469])|(11))-?((0?[1-9])|([1-2][0-9])|(30)))|");
reg.append("(0?2-?((0?[1-9])|([1-2][0-9])))))|(\\d{2}(([02468][12");
reg.append("35679])|([13579][01345789]))-?((((0?[13578])|(1[02]))");
reg.append("-?((0?[1-9])|([1-2][0-9])|(3[01])))|(((0?[469])|(11))");
reg.append("-?((0?[1-9])|([1-2][0-9])|(30)))|(0?2-?((0?[");
reg.append("1-9])|(1[0-9])|(2[0-8]))))))");
Pattern p = Pattern.compile(reg.toString());
return p.matcher(date).matches();
}
/*****
* 时间 增加、减少 n个小时以后时间
**/
public static Date adjustDateByHour(Date d, Integer num, int type) {
Calendar Cal = Calendar.getInstance();
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Cal.setTime(d);
if (type == 0) {
Cal.add(Calendar.MINUTE, -num);
// System.out.println("date:"+df.format(Cal.getTime()));
} else {
Cal.add(Calendar.MINUTE, num);
// System.out.println("date:"+df.format(Cal.getTime()));
}
return Cal.getTime();
}
/*****
* 时间 增加、减少 n个分钟以后时间
**/
public static Date adjustDateByMinutes(Date d, Integer num, int type) {
Calendar Cal = Calendar.getInstance();
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Cal.setTime(d);
if (type == 0) {
Cal.add(Calendar.MINUTE, -num);
// System.out.println("date:"+df.format(Cal.getTime()));
} else {
Cal.add(Calendar.MINUTE, num);
// System.out.println("date:"+df.format(Cal.getTime()));
}
return Cal.getTime();
}
}