日期操作，方法收藏

package com;

import java.math.BigDecimal;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;

//import org.apache.log4j.Logger;
import org.springframework.jdbc.core.JdbcTemplate;

import com.hotent.core.util.AppUtil;
import com.runqianapp.group.domain.newGroupSheetLoader;

public class HyReportUtil {
// private Logger log = Logger.getLogger(HyReportUtil.class);
private static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
private static SimpleDateFormat sdfYear = new SimpleDateFormat("yyyy");

/**
* 获取年的第几天，getDAY_OF_YEAR
*/
public static int getDAY_OF_YEAR(String rq) throws Exception {
int num =0;
Calendar c = Calendar.getInstance();
c.setTime(sdf.parse(rq));
num=c.get(Calendar.DAY_OF_YEAR);
return num;
}
/**
* 获取月的第几天，getDAY_OF_MONTH
*/
public static int getDAY_OF_MONTH(String rq) throws Exception {
int num =0;
Calendar c = Calendar.getInstance();
c.setTime(sdf.parse(rq));
num=c.get(Calendar.DAY_OF_MONTH);
return num;
}

/**
* 字符串的日期加上一天，在返回字符串
*/
public static String addOneDay(String countdate) throws Exception {
Calendar c = Calendar.getInstance();
c.setTime(sdf.parse(countdate));
c.add(Calendar.DATE, 1);
String rtn = sdf.format(c.getTime());
return rtn;
}

/**
* 字符串的日期减去一天，在返回字符串
*/
public static String subOneDay(String countdate) throws Exception {
Calendar c = Calendar.getInstance();
c.setTime(sdf.parse(countdate));
c.add(Calendar.DATE, -1);
String rtn = sdf.format(c.getTime());
return rtn;
}

/**
* @param rq 字符串的日期 格式 yyyy-MM-dd
* @param num
* @return 添加或减去它的天数，在返回字符串
* @throws Exception
* String
*
*/
public static String addOrSubRq(String rq,int num) throws Exception {
Calendar c = Calendar.getInstance();
c.setTime(sdf.parse(rq));
c.add(Calendar.DATE, num);
String rtn = sdf.format(c.getTime());
return rtn;
}

/**
* @param tjrq
* @return yyyy-MM-dd 格式化为 yyyyMMdd
*/
public static String formatDateForyyyyMMdd(String tjrq) throws Exception {
Date date = sdf.parse(tjrq);
tjrq = new SimpleDateFormat("yyyyMMdd").format(date);
return tjrq;
}

/**
* @param tjrq
* @return yyyy-MM-dd 格式化为 yyyy
*/
public static String formatDateForYYYY(String tjrq) throws Exception {
Date date = sdfYear.parse(tjrq);
tjrq = new SimpleDateFormat("yyyy").format(date);
return tjrq;
}
/**
* @param tjrq
* @return yyyy-MM-dd 格式化为 yyyyMM
*/
public static String formatDateForyyyyMM(String tjrq) throws Exception {
Date date = sdf.parse(tjrq);
tjrq = new SimpleDateFormat("yyyyMM").format(date);
return tjrq;
}

/**
* @param tjrq
* @return 将字符串日期减去一年
* @throws Exception
* String
*
*/
public static String subOneYearForDate(String tjrq) throws Exception {
Date date = sdf.parse(tjrq);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.YEAR, -1);
tjrq = sdf.format(calendar.getTime());

return tjrq;
}

/**
* @param tjrq
* @return 将字符串日期减去一个月
* @throws Exception
* String
*
*/
public static String subOneMonthForDate(String tjrq) throws Exception {
Date date = sdf.parse(tjrq);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.MONTH, -1);
tjrq = sdf.format(calendar.getTime());
return tjrq;
}

/**
* @param tjrq 参数格式为yyyy-MM-dd
* @param type 参数 只能为month 或year
* @throws Exception
* 循环遍历，当月或当年日期，并返回list集合
*
*/
public static List<String> traversalMonthOrYear(String tjrq,String type) throws Exception {
List<String> list= new ArrayList<String>();
Calendar c = Calendar.getInstance();
int dayNum = 0;
if ("month".equals(type)) {
dayNum = HyReportUtil.getDAY_OF_MONTH(sdf.format(c.getTime()));
}else if("year".equals(type)){
dayNum = HyReportUtil.getDAY_OF_YEAR(sdf.format(c.getTime()));
}
for (int i = 1; i < dayNum; i++) {
c.add(Calendar.DATE, -1);
list.add(sdf.format(c.getTime()));
}
return list;

}


/**
* @param args
* @throws Exception
* void
*
*/
public static void main(String[] args) throws Exception {

// traversalMonthOrYear("2020-03-08","month");

System.out.println(traversalMonthOrYear("2020-03-08","year"));

// System.out.println(getDAY_OF_MONTH("2020-03-08"));
// System.out.println(getDAY_OF_YEAR("2020-03-08"));
// System.out.println(getDAY_OF_YEAR("2019-12-25"));

}
}