是否有一种简单的方法来检查null的字段是否使用

Question

我有一个带有三对Date字段的类。

public static final class Filter {
    private final Date startDateFrom;
    private final Date startDateTo;
    private final Date endDateFrom;
    private final Date endDateTo;
    private final Date regDateFrom;
    private final Date regDateTo;
    public Filter(Date startDateFrom, Date startDateTo, 
                  Date endDateFrom, Date endDateTo, 
                  Date regDateFrom, Date regDateTo) {
        this.startDateFrom = startDateFrom;
        this.startDateTo = startDateTo;
        this.endDateFrom = endDateFrom;
        this.endDateTo = endDateTo;
        this.regDateFrom = regDateFrom;
        this.regDateTo = regDateTo;
    }
}

因此，我需要检查至少一对没有null日期，并检查DateFrom是否在之前或等于DateTo。

我已经这样做是为了检查至少有一对：

public boolean allDatesMissing() {
        if (startDateFrom != null && startDateTo != null) {
            return false;
        } else if (endDateFrom != null && endDateTo != null) {
            return false;
        } else if (regDateFrom != null && regDateTo != null) {
            return false;
        }
        return true;
    }

这是检查fromDate之前的toDate：

public void checkDates(Date from, Date to) throws RequestException{
    if (from != null) {
        if (to != null) {
            if (from.after(to)) {
                throw new MyException(INCORRECT_DATES_PERIOD);
            }
        } else {
            throw new MyException(MISSING_PARAMETER);
        }
    } else if (to != null){
        throw new MyException(MISSING_PARAMETER);
    }
}

是否有更简单的方法可以做相同的方法？

Answer 1

您已经声明了滤波器类静态。

package demo;
import java.util.Date;
public class FilterDemo {
public static void main(String[] args) throws Exception {
    Filter f = new Filter(new Date(2017, 01, 01), new Date(2017, 02, 01),
            null, null, null, null);
}
public static final class Filter {
    private final Date startDateFrom;
    private final Date startDateTo;
    private final Date endDateFrom;
    private final Date endDateTo;
    private final Date regDateFrom;
    private final Date regDateTo;
    // dateCounter will maintain the count of correct date pair
    public static int dateCount = 0;
    public Filter(Date startDateFrom, Date startDateTo, Date endDateFrom,
            Date endDateTo, Date regDateFrom, Date regDateTo)
            throws Exception {
        this.startDateFrom = startDateFrom;
        this.startDateTo = startDateTo;
        isExist(startDateFrom, startDateTo);
        this.endDateFrom = endDateFrom;
        this.endDateTo = endDateTo;
        isExist(endDateFrom, endDateTo);
        this.regDateFrom = regDateFrom;
        this.regDateTo = regDateTo;
        isExist(regDateFrom, regDateTo);
        //  throw exception after initializing 3 pair,if count is still 0
        if (dateCount == 0)
            throw new Exception("All pairs are null");
    }
    public static void isExist(Date from, Date to) throws Exception {
        if (from != null && to != null) {
            checkDates(from, to);
        }
    }
    public static void checkDates(Date from, Date to) throws Exception {
        if (from.getTime() > to.getTime()) {
            throw new Exception("INCORRECT_DATES_PERIOD");
        }
        //increase dateCount if date pair is correct
        dateCount++;
    }
}
}