How to group times in Unix-time by day?

Question

Java

Hello.
There is a collection of entities (conditionally an event), which have a field This field stores time in UnixTime format. I need to count the number of events that happened in days. That is, ideally, you want to get at the output , where the key is the day (just a day, without time), and the value is the number of events. And something I have an algorithmic plug. I feel that I need to write a function for , which takes UnixTime as input, and gives a date without time as output. But at the same time, I also want it so that the comparison of the date is only year-month-day, so that you can then group the .
Long time; // System.currentTimeInMillis()
Map<Date, Integer>
stream().map()Collectors.groupBy()
Actually, the question is - is there a ready-made class that stores only the date (without time) and / or which implements equals taking into account the date without time. Or do you have to write your own wrapper?

Answer 1

Unix-time - you mean the number of ml.sec. from 01/01/1970?
Then just divide the value by the number of milliseconds in a day (86400000) to get the same unix-time in days only.