Check if date is one week before from today Java

Issue

I am trying to check if a particular date is one week before from today's date. I formatted my date into this format:

SimpleDateFormat formatter = new SimpleDateFormat("MM/dd/yyyy hh:mm a");

Then, I get the list of date from a for loop by these code:

Date formattedToday = formatter.parse(todayStr);
Date formattedExpired = formatter.parse(expiredDate);

The example of dates in the list are:

09/12/2017 08:09 PM
10/24/2015 02:09 AM
07/18/2018 03:10 AM

I tried to follow this thread but I am not allowed to add in any external libraries.

The other solution that requires Java 8 is not applicable for me also as my current min API is 25 but ChronoUnit requires API 26.

Any ideas? Thanks!

Solution

Using only Date and Calendar classes (and thus, compatible with any JVM from about 4-ish, I think?) you could try this sort of solution:

1. Get today as a Date: Date now = new Date()
2. Get one week ago from that, as a Calendar: Calendar expected = Calendar.getInstance(); expected.setTime(now); lastWeek.add(Calendar.WEEK_OF_YEAR, -1);
3. Get your expired date as a Calendar: Calendar actual = Calendar.getInstance().setTime(expiredDate);
4. Compare the year and day of year of the two calendars (you can compare other fields, but those two should be enough): return (expected.get(Calendar.YEAR) == actual.get(Calendar.YEAR)) && (expected.get(Calendar.WEEK_OF_YEAR) == actual.get(Calendar.WEEK_OF_YEAR));

Using this, you should be able to come up with an even shorter snippet that subtracts a week from now and compares the long values of the two. Though obviously that wouldn't be comparing calendar dates, it would be comparing nanoseconds :)

Answered By - Paul Hicks