Keep last week worth of substring dates from current day in java?

Question

Suppose we have a bunch of files in a list and their names consisted of file + a date and time format in the form of dd_mm_yyyy_hour_minute_second. It would look something like this:

[
file_03_12_20_23_11_42
file_29_11_20_23_11_42
file_28_11_20_23_31_41
file_11_11_19_23_31_12
file_23_06_19_23_11_35
file_02_12_20_23_50_31
file_30_11_20_23_41_12
...
]

Is there a way to filter through this list to keep anything within the last week from the current date?

I know how to grab the current date with either the Date class or Calender class, but I have no idea how to keep the last 7 days of these files. This is List of type File, but the file names are going to be strings when using file.toString().

Answer 1

Say you have a directory of files, like so:

Users/Shash/Desktop/Files
 ├── file_02_12_20_23_50_31
 ├── file_03_12_20_23_11_42
 ├── file_11_11_19_23_31_12
 ├── file_23_06_19_23_11_35
 ├── file_28_11_20_23_31_41
 ├── file_29_11_20_23_11_42
 └── file_30_11_20_23_41_12

You could use parse LocalDate's from the file names and filter the ones that are before the LocalDate corresponding to one week ago:

import java.io.File;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Locale;
import java.util.Objects;

class Main {
    public static void main(String[] args) {
        File fileDirectory = new File("/Users/Shash/Desktop/Files");
        List<File> filesWithDates =
                Arrays.asList(Objects.requireNonNull(fileDirectory.listFiles()));

        System.out.println("Before filtering:");
        filesWithDates.forEach(f -> System.out.println(f.getName()));

        List<File> filesWithDatesUpToWeekOld = filterOldFiles(filesWithDates);

        System.out.println("After filtering:");
        filesWithDatesUpToWeekOld.forEach(f -> System.out.println(f.getName()));
    }

    private static List<File> filterOldFiles(List<File> filesWithDates) {
        List<File> filteredFiles = new ArrayList<>();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern(
                "'file'_dd_MM_yy_HH_mm_ss", Locale.ENGLISH);
        LocalDate oneWeekAgo = LocalDate.now().minus(1, ChronoUnit.WEEKS);
        for (File fileWithDate : filesWithDates) {
            LocalDate dateTime = LocalDate.parse(fileWithDate.getName(), formatter);
            if (!dateTime.isBefore(oneWeekAgo)) {
                filteredFiles.add(fileWithDate);
            }
        }
        return filteredFiles;
    }
}

Output:

Before filtering:
file_30_11_20_23_41_12
file_03_12_20_23_11_42
file_23_06_19_23_11_35
file_28_11_20_23_31_41
file_11_11_19_23_31_12
file_29_11_20_23_11_42
file_02_12_20_23_50_31
After filtering:
file_30_11_20_23_41_12
file_03_12_20_23_11_42
file_28_11_20_23_31_41
file_29_11_20_23_11_42
file_02_12_20_23_50_31