Java自定义日期处理工具类

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1、主要使用Calendar类、SimpleDateFormat类
2、同时注意add方法是相对当前月而言的，而set方法是对应整体而言，整体是月就是从月的第一天开始，是年就从年的第一天开始
3、工具类代码如下：
public class CalendarUtil {    publicstatic final String FORMAT_1="yyyyMMdd";    publicstatic final String FORMAT_2="yyyy-MM-dd";    publicstatic final String FORMAT_3="yyyy-MM-dd hh:mm:ss";    publicstatic final String FORMAT_4="yyyyMMdd hh:mm:ss";      //获取当前日期    publicString getNow(String stringType){       Calendarcalendar=Calendar.getInstance();       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取前/后几天的日期    publicString getLastOrNextDate(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.DAY_OF_YEAR, i);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取这周某天日期    publicString getOneDateOfWeek(int i,String stringType){       Calendarcalendar=Calendar.getInstance();            if(calendar.get(Calendar.DAY_OF_WEEK)!=1){          if (i<=6){            calendar.set(Calendar.DAY_OF_WEEK, i+1);          }else if(i==7) {            calendar.add(Calendar.WEEK_OF_MONTH, 1);            calendar.set(Calendar.DAY_OF_WEEK, 1);          }       }else{          if (i<=6){            calendar.add(Calendar.WEEK_OF_MONTH, -1);            calendar.set(Calendar.DAY_OF_WEEK, i+1);          }else if(i==7) {            calendar.set(Calendar.DAY_OF_WEEK, 1);          }       }       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取前/后第几周日期    publicString getLastOrNextWeek(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.WEEK_OF_MONTH, i);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取前/后几个月对应日期    publicString getlastOrNextDateOfMonth(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.MONTH, i);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取某月某一天日期    publicString getOneDateOfMonth(int i,int j,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.MONTH, i);      calendar.set(Calendar.DAY_OF_MONTH, j);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取某月第一天日期    publicString getFirstDateOfMonth(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.MONTH, i);      calendar.set(Calendar.DAY_OF_MONTH, 1);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取某月最后一天日期    publicString getLastDateOfMonth(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.MONTH, i+1);      calendar.set(Calendar.DAY_OF_MONTH, 0);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取某月第一天零点日期时间    public DategetFirstDateTimeZoreOfMonth(int i,String stringType) throwsParseException{       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.MONTH, i);      calendar.set(Calendar.DAY_OF_MONTH, 1);       return newSimpleDateFormat(stringType).parse(newSimpleDateFormat(stringType).format(calendar.getTime()));    }      //获取前/后几年的日期    publicString getlastOrNextDateOfYear(int i,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.YEAR, i);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }      //获取某年第几天的日期    publicString getOneDateOfYear(int i,int j,String stringType){       Calendarcalendar=Calendar.getInstance();      calendar.add(Calendar.YEAR, i);      calendar.set(Calendar.DAY_OF_YEAR, j);       return newSimpleDateFormat(stringType).format(calendar.getTime());    }}在写个测试用例：public class MainTest {       publicstatic void main(String[] args) throws ParseException {       CalendarUtilcalendarUtil=new CalendarUtil();            System.out.println(calendarUtil.getFirstDateTimeZoreOfMonth(0,CalendarUtil.FORMAT_4));            System.out.println(calendarUtil.getFirstDateOfMonth(0,CalendarUtil.FORMAT_1));            System.out.println(calendarUtil.getLastDateOfMonth(0,CalendarUtil.FORMAT_1));            System.out.println(calendarUtil.getOneDateOfMonth(0,4,CalendarUtil.FORMAT_1));            System.out.println(calendarUtil.getOneDateOfWeek(1,CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getNow(CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getLastOrNextWeek(1,CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getlastOrNextDateOfMonth(0,CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getLastOrNextDate(-1,CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getlastOrNextDateOfYear(-1,CalendarUtil.FORMAT_2));            System.out.println(calendarUtil.getOneDateOfYear(0,40,CalendarUtil.FORMAT_1));    }}
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