java中一个集合里面的对象按照里面的一个属性，这个属性是时间，按时间倒叙收集成集合，然后按照时间相同的分组，并且要按照顺序拿出来每一组

可以使用Java 8的Stream API来完成这个任务。首先，我们需要按照时间倒序排序集合，然后使用`Collectors.groupingBy()`方法将对象按照时间分组，最后使用`LinkedHashMap`来保持分组后的顺序。

以下是示例代码：

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

        List<MyObject> objects = Arrays.asList(
                new MyObject("A", LocalDateTime.parse("2021-01-01 10:00:00", formatter)),
                new MyObject("B", LocalDateTime.parse("2021-01-02 10:00:00", formatter)),
                new MyObject("C", LocalDateTime.parse("2021-01-02 10:00:00", formatter)),
                new MyObject("D", LocalDateTime.parse("2021-01-03 10:00:00", formatter)),
                new MyObject("E", LocalDateTime.parse("2021-01-03 10:00:00", formatter)),
                new MyObject("F", LocalDateTime.parse("2021-01-03 11:00:00", formatter))
        );

        Map<LocalDateTime, List<MyObject>> groupedObjects = objects.stream()
                .sorted((o1, o2) -> o2.getTime().compareTo(o1.getTime()))
                .collect(Collectors.groupingBy(MyObject::getTime, LinkedHashMap::new, Collectors.toList()));

        groupedObjects.forEach((time, list) -> {
            System.out.println("Time: " + time);
            list.forEach(System.out::println);
            System.out.println();
        });
    }
}

class MyObject {
    private String name;
    private LocalDateTime time;

    public MyObject(String name, LocalDateTime time) {
        this.name = name;
        this.time = time;
    }

    public String getName() {
        return name;
    }

    public LocalDateTime getTime() {
        return time;
    }

    @Override
    public String toString() {
        return "MyObject{" +
                "name='" + name + '\'' +
                ", time=" + time +
                '}';
    }
}

输出结果：

Time: 2021-01-03T11:00
MyObject{name='F', time=2021-01-03T11:00}

Time: 2021-01-03T10:00
MyObject{name='D', time=2021-01-03T10:00}
MyObject{name='E', time=2021-01-03T10:00}

Time: 2021-01-02T10:00
MyObject{name='B', time=2021-01-02T10:00}
MyObject{name='C', time=2021-01-02T10:00}

Time: 2021-01-01T10:00
MyObject{name='A', time=2021-01-01T10:00}