Code/Projects/DateWriter/DateWriter.java

   1 import java.io.File;
   2 import java.io.BufferedReader;
   3 import java.io.FileReader;
   4 import java.io.PrintWriter;
   5 import java.time.LocalDate;
   6 import java.time.LocalTime;
   7 import java.time.format.DateTimeFormatter;
   8 import java.io.IOException;
   9
  10 public class DateWriter {
  11
  12         public static void main(String[] args) throws IOException {
  13                 if (args.length < 3) {
  14                         System.out.println("Usage: java " + DateWriter.class.getSimpleName() + " /path/to/file/with/timestamps /path/to/new/timestamp/file/with/dates initial_date_in_MM/dd/uuuu_format");
  15                         System.exit(1);
  16                 }
  17                 String pathOriginal = args[0];
  18                 String pathModified = args[1];
  19                 String initialDateStr = args[2];
  20                 DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("MM/dd/uuuu");
  21                 LocalDate date = LocalDate.parse(initialDateStr, dateFormatter);
  22                 File originalFile = new File(pathOriginal);
  23                 // Create output file
  24                 File modifiedFile = new File(pathModified);
  25                 modifiedFile.createNewFile();
  26                 BufferedReader reader = new BufferedReader(new FileReader(originalFile));
  27                 PrintWriter writer = new PrintWriter(modifiedFile);
  28                 String line = null;
  29                 String prevLine = null;
  30                 while ((line = reader.readLine()) != null) {
  31                         if (isNewDay(line, prevLine)) {
  32                                 // Advance date
  33                                 date = date.plusDays(1);
  34                         }
  35                         writer.println(String.format("%s %s", date.format(dateFormatter), line));
  36                         prevLine = line;
  37                 }
  38                 writer.flush();
  39                 writer.close();
  40                 reader.close();
  41         }
  42
  43         private static boolean isNewDay(String line, String prevLine) {
  44                 if (prevLine == null) {
  45                         return false;
  46                 }
  47                 // First part handles case where we pass midnight and the following timestamp is an AM timestamp
  48                 // Second case handles case where we pass midnight, but the following timestamp is a PM timestamp
  49                 return line.endsWith("AM") && prevLine.endsWith("PM") || toLocalTime(line).isBefore(toLocalTime(prevLine));
  50         }
  51
  52         private static LocalTime toLocalTime(String timeString) {
  53                 return LocalTime.parse(timeString, DateTimeFormatter.ofPattern("h:mm:ss a"));
  54         }
  55 }