Java时间日期格式转换Date转String和String转Date

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class DateUtil {

    private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

    /*
	获取昨天的日期
	 */
    public static Date getYesterday(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.add(Calendar.DATE,-1);
        Date yesterday = cal.getTime();
        return yesterday;
    }

    /*
    获取传入时间的日份
     */
    public static int getDay(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        return cal.get(Calendar.DATE);
    }

    /**
     * 获取传入时间的月份
     */
    public static int getMonth(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        return cal.get(Calendar.MONTH) + 1;
    }

    /**
     * 获取传入时间的季度
     */
    public static int getQuarter(Date date) {
        int month = getMonth(date);
        if (month <= 3)
            return 1;
        else if (month <= 6)
            return 2;
        else if (month <= 9)
            return 3;
        else
            return 4;
    }

    /**
     * 获取传入时间的年份
     */
    public static int getYear(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        return cal.get(Calendar.YEAR);
    }

    /**
     * 获取传入时间月份天数
     */
    public static int getCurrentMonthDay(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.set(Calendar.DATE, 1);
        cal.roll(Calendar.DATE, -1);
        return cal.get(Calendar.DATE);
    }

    /**
     * 获得传入时间为是星期几
     */
    public static int getWeekDay(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        int weekDay = c.get(Calendar.DAY_OF_WEEK);
        return weekDay - 1;
    }

    /*
    获取所在周指定星期几的日期Date
     */
    public static Date getWeekDayDate(Date date, int num) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        switch (num) {
            case 1:
                c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
                break;
            case 2:
                c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
                break;
            case 3:
                c.set(Calendar.DAY_OF_WEEK, Calendar.WEDNESDAY);
                break;
            case 4:
                c.set(Calendar.DAY_OF_WEEK, Calendar.THURSDAY);
                break;
            case 5:
                c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
                break;
            case 6:
                c.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
                break;
            case 7:
                // c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
                int weekday = c.get(Calendar.DAY_OF_WEEK);
                c.add(Calendar.DATE, 8 - weekday);
                break;
        }
        return c.getTime();
    }

    /*
    获取传入时间所在周第一天，周一
     */
    public static Date getFirstWeekDay(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        try {
            int weekday = c.get(Calendar.DAY_OF_WEEK) - 2;
            c.add(Calendar.DATE, -weekday);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return c.getTime();
    }

    /*
    获取传入时间所在周最后一天，周日
     */
    public static Date getLastWeekDay(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        try {
            int weekday = c.get(Calendar.DAY_OF_WEEK);
            c.add(Calendar.DATE, 8 - weekday);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return c.getTime();
    }

    /**
     * 根据日期获取月初第一天
     */
    public static Date getFirstMonthDay(Date date) {
        Calendar cal = Calendar.getInstance();// 获取当前日期
        cal.setTime(date);
        cal.add(Calendar.MONTH, 0);
        cal.set(Calendar.DAY_OF_MONTH, 1);
        return cal.getTime();
    }

    /**
     * 根据日期获取月末最后一天
     */
    public static Date getLastMonthDay(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
        return cal.getTime();
    }

    /*
    根据日期获取所在季度的第一天
     */
    public static Date getFirstQuarterDay(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int currentMonth = cal.get(Calendar.MONTH) + 1;
        try {
            if (currentMonth >= 1 && currentMonth <= 3)
                cal.set(Calendar.MONTH, 0);
            else if (currentMonth >= 4 && currentMonth <= 6)
                cal.set(Calendar.MONTH, 3);
            else if (currentMonth >= 7 && currentMonth <= 9)
                cal.set(Calendar.MONTH, 6);
            else if (currentMonth >= 10 && currentMonth <= 12)
                cal.set(Calendar.MONTH, 9);
            cal.set(Calendar.DAY_OF_MONTH, cal.getActualMinimum(Calendar.DAY_OF_MONTH));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return cal.getTime();
    }

    /*
    根据日期获取所在季度的最后一天
     */
    public static Date getLastQuarterDay(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int currentMonth = cal.get(Calendar.MONTH) + 1;
        try {
            if (currentMonth >= 1 && currentMonth <= 3)
                cal.set(Calendar.MONTH, 2);
            else if (currentMonth >= 4 && currentMonth <= 6)
                cal.set(Calendar.MONTH, 5);
            else if (currentMonth >= 7 && currentMonth <= 9)
                cal.set(Calendar.MONTH, 8);
            else if (currentMonth >= 10 && currentMonth <= 12)
                cal.set(Calendar.MONTH, 11);
            cal.set(Calendar.DAY_OF_MONTH, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return cal.getTime();
    }

    /*
    所在年前/后半年开始日期
     */
    public static Date getHalfYearStartTime(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        int currentMonth = c.get(Calendar.MONTH) + 1;
        if (currentMonth >= 1 && currentMonth <= 6) {
            c.set(Calendar.MONTH, 0);
        } else if (currentMonth >= 7 && currentMonth <= 12) {
            c.set(Calendar.MONTH, 6);
        }
        c.set(Calendar.DATE, 1);
        return c.getTime();
    }

    /**
     所在年前/后半年的结束时间
     */
    public static Date getHalfYearEndTime(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        int currentMonth = c.get(Calendar.MONTH) + 1;
        if (currentMonth >= 1 && currentMonth <= 6) {
            c.set(Calendar.MONTH, 5);
            c.set(Calendar.DATE, 30);
        } else if (currentMonth >= 7 && currentMonth <= 12) {
            c.set(Calendar.MONTH, 11);
            c.set(Calendar.DATE, 31);
        }
        return c.getTime();
    }

    /**
     * 根据日期获取年第一天
     */
    public static Date getYearFirstDay(Date date){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int year=calendar.get(Calendar.YEAR);
        Calendar cd = Calendar.getInstance();
        cd.clear();
        cd.set(Calendar.YEAR, year);
        cd.roll(Calendar.DAY_OF_YEAR,0);
        Date currYearLast = cd.getTime();
        return currYearLast;
    }

    /*
	获取当月指定天数日期
	 */
    public static Date getDateByDay(Date date, int day) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        cal.set(Calendar.DATE, day);
        return cal.getTime();
    }

    /*
	获取上月指定天数日期
	 */
    public static Date getLastMonthByDay(Date date, int day) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int month = cal.get(Calendar.MONTH);
        cal.set(Calendar.MONTH, month - 1);
        cal.set(Calendar.DATE, day);
        return cal.getTime();
    }

    /**
     * 获取传入时间所在季度总天数
     */
    public static int getCurrentQuarterDay(Date date) {
        Date firstDayDate = getFirstQuarterDay(date);
        Date lastDayDate = getLastQuarterDay(date);
        int day = (int) ((lastDayDate.getTime() - firstDayDate.getTime()) / (24*3600*1000) + 1);
        return day;
    }

    /*
    判断日期是否为周日
     */
    public static boolean isWeekEnd(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        if(calendar.get(Calendar.DAY_OF_WEEK) == Calendar.SUNDAY){
            return true;
        } else{
            return false;
        }
    }

    /*
    判断日期是否为月末
     */
    public static boolean isMonthEnd(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int getDay = calendar.get(Calendar.DAY_OF_MONTH);
        if(getDay == calendar.getActualMaximum(Calendar.DAY_OF_MONTH)){
            return true;
        }else{
            return false;
        }
    }

    /*
    判断日期是否为季末（最后一天）
     */
    public static boolean isQuarterEnd(Date date) {
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        int currentMonth = c.get(Calendar.MONTH) + 1;
        Date dt = null;
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        try {
            if (currentMonth >= 1 && currentMonth <= 3) {
                c.set(Calendar.MONTH, 2);
                c.set(Calendar.DATE, 31);
            } else if (currentMonth >= 4 && currentMonth <= 6) {
                c.set(Calendar.MONTH, 5);
                c.set(Calendar.DATE, 30);
            } else if (currentMonth >= 7 && currentMonth <= 9) {
                c.set(Calendar.MONTH, 8);
                c.set(Calendar.DATE, 30);
            } else if (currentMonth >= 10 && currentMonth <= 12) {
                c.set(Calendar.MONTH, 11);
                c.set(Calendar.DATE, 31);
            }
            dt = sdf.parse(sdf.format(c.getTime()));
        } catch (Exception e) {
            e.printStackTrace();
        }
        if (date.compareTo(dt) == 0) {
            return true;
        } else {
            return false;
        }
    }

    /*
    据日期获取去年年末
     */
    public static Date getLastYearLastDay(Date date){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int year=calendar.get(Calendar.YEAR)-1;
        Calendar cd = Calendar.getInstance();
        cd.clear();
        cd.set(Calendar.YEAR, year);
        cd.roll(Calendar.DAY_OF_YEAR, -1);
        Date currYearLast = cd.getTime();
        return currYearLast;
    }

    /**
     * 属于本年第几天
     */
    public static int getYearDayIndex(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setFirstDayOfWeek(Calendar.MONDAY);
        calendar.setTime(date);
        return calendar.get(Calendar.DAY_OF_YEAR);
    }

    /**
     * 属于本年第几周
     */
    public static int getYearWeekIndex(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setFirstDayOfWeek(Calendar.MONDAY);
        calendar.setTime(date);
        return calendar.get(Calendar.WEEK_OF_YEAR);
    }

    /*
    获取两个日期间的天数,直接传入Date
     */
    public static Long getDayByDates(Date startDate, Date endDate) {
        Long day = (endDate.getTime() - startDate.getTime()) / (24 * 60 * 60 * 1000);
        return day;
    }

    /*
    获取两个日期间的天数，直接传入StrDate
     */
    public static Long getDayByStrDates(String startStrDate, String endStrDate) throws ParseException {
        Date startDate = sdf.parse(startStrDate);
        Date endDate = sdf.parse(endStrDate);
        Long day = (endDate.getTime() - startDate.getTime()) / (24 * 60 * 60 * 1000);
        return day;
    }

    /**
     * 判断是否闰年
     * 详细设计： 1.被400整除是闰年，否则： 2.不能被4整除则不是闰年 3.能被4整除同时不能被100整除则是闰年
     *            3.能被4整除同时能被100整除则不是闰年
     */
    public static boolean isLeapYear(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int year = cal.get(Calendar.YEAR);
        if ((year % 400) == 0) {
            return true;
        } else if ((year % 4) == 0) {
            if ((year % 100) == 0) {
                return false;
            } else {
                return true;
            }
        } else {
            return false;
        }
    }

    public static void main(String[] args) throws ParseException {
        Date date = new Date();
        System.out.println("前一天日期为：" + sdf.format(getYesterday(date)));
        System.out.println("该日期的日份：" + getDay(date));
        System.out.println("该日期的月份：" + getMonth(date));
        System.out.println("该日期的季度：" + getQuarter(date));
        System.out.println("该日期的年份：" + getYear(date));
        System.out.println("所在月总天数：" + getCurrentMonthDay(date));
        System.out.println("所在季度总天数：" + getCurrentQuarterDay(date));
        System.out.println("该日期为本周星期：" + getWeekDay(date));
        System.out.println("所在周的星期天的日期：" + sdf.format(getWeekDayDate(date, 7)));
        System.out.println("所在周第一天日期：" + sdf.format(getFirstWeekDay(date)));
        System.out.println("所在周最后一天日期：" + sdf.format(getLastWeekDay(date)));
        System.out.println("所在月第一天日期：" + sdf.format(getFirstMonthDay(date)));
        System.out.println("所在月最后一天日期：" + sdf.format(getLastMonthDay(date)));
        System.out.println("所在季度第一天日期：" + sdf.format(getFirstQuarterDay(date)));
        System.out.println("所在季度最后一天日期：" + sdf.format(getLastQuarterDay(date)));
        System.out.println("所在年前/后半年开始日期：" + sdf.format(getHalfYearStartTime(date)));
        System.out.println("所在年前/后半年结束日期：" + sdf.format(getHalfYearEndTime(date)));
        System.out.println("所在年第一天日期：" + sdf.format(getYearFirstDay(date)));
        System.out.println("所在月指定天数日期：" + sdf.format(getDateByDay(date, 10)));
        System.out.println("上月指定天数日期：" + sdf.format(getLastMonthByDay(date, 10)));
        System.out.println("是否为周日：" + isWeekEnd(date));
        System.out.println("是否为月末：" + isMonthEnd(date));
        System.out.println("是否为季末：" + isQuarterEnd(date));
        System.out.println("去年最后一天日期：" + sdf.format(getLastYearLastDay(date)));
        System.out.println("属于本年第几天：" + getYearDayIndex(date));
        System.out.println("属于本年第几周：" + getYearWeekIndex(date));
        System.out.println("两个日期的间隔天数：" + getDayByDates(sdf.parse("2019-10-28"), date));
        System.out.println("两个日期的间隔天数：" + getDayByStrDates("2019-10-23", "2019-10-30"));
        System.out.println("是否为闰年：" + isLeapYear(date));
    }
}

　　测试结果：

前一天日期为：2019-10-29
该日期的日份：30
该日期的月份：10
该日期的季度：4
该日期的年份：2019
所在月总天数：31
所在季度总天数：92
该日期为本周星期：3
所在周的星期天的日期：2019-11-03
所在周第一天日期：2019-10-28
所在周最后一天日期：2019-11-03
所在月第一天日期：2019-10-01
所在月最后一天日期：2019-10-31
所在季度第一天日期：2019-10-01
所在季度最后一天日期：2019-12-31
所在年前/后半年开始日期：2019-07-01
所在年前/后半年结束日期：2019-12-31
所在年第一天日期：2019-01-01
所在月指定天数日期：2019-10-10
上月指定天数日期：2019-09-10
是否为周日：false
是否为月末：false
是否为季末：false
去年最后一天日期：2018-12-31
属于本年第几天：303
属于本年第几周：44
两个日期的间隔天数：2
两个日期的间隔天数：7
是否为闰年：false