日期计算方法中的Java日期转换问题

Question

我曾尝试用Java创建一个方法，它将获取当前日期或存储的日期，并在之前或之后获取x天

//28 days ago
java.util.Date thresholdPast28Date  = BasicUtils.setTimeInDays(sqlTodayDate, -28);

//56 days ago
java.util.Date thresholdPast56Date  = BasicUtils.setTimeInDays(sqlTodayDate, -56);

函数如下所示

public static Date setTimeInDays(Date startingTime, Integer days){
    Calendar c = Calendar.getInstance(); 
    c.setTime(startingTime); 
    c.add(Calendar.DATE, days);//a day in the future or past
    return c.getTime();
}

虽然我试图把今天的日期推到这个方法中，但还是会出错

java.util.Date cannot be cast to java.sql.Date

--今天就这样约会

//today date
Calendar today = Calendar.getInstance(); 
Date sqlTodayDate =  (Date) today.getTime();