hadoop UDF-获取前N周的日期时间点

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应用场景：获取前N周的日期，且需要指定星期值（如周一、周二）。例如，获取前面第N个星期三当天的日期
输入：1. 初始化日期，即从哪个日期值开始往前查询(支持 yyyyMMdd, yyyy-MM-dd, yyyy-MM-dd hh:mi:ss)；2. 周区间的个数；3. 指定星期值（仅限于缩写 "SUN","MON","TUE","WED","THU","FRI","SAT"）

输出：日期值，格式 yyyy-MM-dd

适用于阿里云MaxCompute平台的UDF源码：

import com.aliyun.odps.udf.UDF;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
 
 
public final class getSpecificNumberWeek extends UDF{
    public String evaluate(String inputDateStr, Long weekNum, String weekName) throws ParseException {
        //先获取输入的日期是一周中第几天
        Date date = null;
        if (inputDateStr.length() == 19) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            date = sdf.parse(inputDateStr);
        } else if (inputDateStr.length() == 10) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            date = sdf.parse(inputDateStr);
        } else if (inputDateStr.length() == 8) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
            date = sdf.parse(inputDateStr);
        }
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        Integer curWeekIndex = cal.get(Calendar.DAY_OF_WEEK);
//        System.out.println(curWeekIndex);
        //获取输入周X是一周中第几天
        List<String> weekList = Arrays.asList("SUN","MON","TUE","WED","THU","FRI","SAT");
        Integer targetWeekIndex = weekList.indexOf(weekName)+1;
//        System.out.println(targetWeekIndex);
        if(targetWeekIndex.equals(-1)){
            System.out.println("INPUT WEEK DAY DOES NOT EXIST");
            return null;
        }
 
        //判断并输出weekNum 个周期前的weekName
        Calendar returnDate = Calendar.getInstance();
        returnDate.setTime(date);
        if(curWeekIndex < targetWeekIndex){
            returnDate.add(Calendar.DAY_OF_MONTH, (-1)*(7*weekNum.intValue() + curWeekIndex+7-targetWeekIndex));
        }else{
            returnDate.add(Calendar.DAY_OF_MONTH, (-1)*(7*weekNum.intValue() + curWeekIndex - targetWeekIndex));
        }
 
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        String returnDateStr = format.format(returnDate.getTime());
 
        return returnDateStr;
    }
}