Joda时间:DateTimeComparator.在Java 8 Time Api中有什么相似之处？

Question

使用Joda Time,您可以做一些非常酷的事情,例如:

package temp;

import org.joda.time.DateTime;
import org.joda.time.DateTimeComparator;
import org.joda.time.DateTimeFieldType;

public class TestDateTimeComparator {

    public static void main(String[] args) {

        //Two DateTime instances which have same month, date, and hour
        //but different year, minutes and seconds

        DateTime d1 = new DateTime(2001,05,12,7,0,0);
        DateTime d2 = new DateTime(2014,05,12,7,30,45);

        //Define the lower limit to be hour and upper limit to be month
        DateTimeFieldType lowerLimit = DateTimeFieldType.hourOfDay();
        DateTimeFieldType upperLimit = DateTimeFieldType.monthOfYear();

        //Because of the upper and lower limits , the comparator shall only consider only those sub-elements
        //within the lower and upper limits i.e.month, day and hour
        //It shall ignore those sub-elements outside the lower and upper limits: i.e year, minute and second
        DateTimeComparator dateTimeComparator = DateTimeComparator.getInstance(lowerLimit,upperLimit);
        int result = dateTimeComparator.compare(d1, d2);

        switch (result) {
        case -1:
            System.out.println("d1 is less than d2");
            break;
        case 0:
            System.out.println("d1 is equal to d2");
            break; 
        case 1:
            System.out.println("d1 is greater than d2");
            break;

        default:
            break;
        }
    }
}

我在这里找到了这个例子.

我想使用Java Time API执行相同的步骤,但不幸的是,我没有看到任何类似的Comparators.

如何仅使用Java Time API比较某些日期和时间字段而不与其他字段进行比较？

Answer 1

您可以使用提供的通用帮助程序方法复制一些此类行为,更多手动Comparator.

假设我们import static java.util.Comparator.comparing;,我们可以定义比较器LocalDateTimes,只比较月份:

Comparator<LocalDateTime> byMonth = comparing(LocalDateTime::getMonth);

或者只比较月,日和小时的那个,如你的例子中所示:

Comparator<LocalDateTime> byHourDayMonth = comparing(LocalDateTime::getMonth) //
  .thenComparing(LocalDateTime::getDayOfMonth) //
  .thenComparing(LocalDateTime::getHour);

这确实让你处于手动决定顺序的位置......不是那么自动但是有一些更精细的控制.