How to sort map of object on the basis of date

Question

How to sort map on the basis of time field in object. My Map looks like:

Map<Integer, ShiftDTO> -> ShiftDTO consist of following key: shiftName, shiftStartTime, shiftEndTime. shiftStartTime is of type Date, and I want to sort on the basis of date in ascending order. Following code I was using to sort on the basis of map key:

LinkedHashMap<Integer, ShiftDTO> sortedMap = new LinkedHashMap<Integer, ShiftDTO>();
    v.getShiftHashMap().entrySet().stream().sorted(Map.Entry.comparingByKey())
        .forEachOrdered(x -> sortedMap.put(x.getKey(), x.getValue()));

But how can I sort all shift entries on the basis of shiftStartTime?

You could use a `TreeMap` for sorting it. Any reason you are using a `LinkedHashMap`? — Nicholas K, Oct 07 '18 at 10:42

score 1 · Accepted Answer · answered Oct 07 '18 at 10:57

You just need to change the comparator in the sorted method. You can use the following comparator:

(entry1, entry2) -> entry1.getValue().shiftStartTime.compareTo(entry2.getValue().shiftStartTime)

Or else you can use a TreeMap and pass this comparator to its constructor while creating the map.

How to sort map of object on the basis of date

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