Memo: [Java] Identify files with an update date of 1 day or less

background

A file that is updated every second is created every day at midnight with a new date. I wanted to identify the latest file other than the file being updated. I will write down the code at that time.

** Get update date **

Get the modified date with File.lastModified (). However, since the returned value is a Long type and a list of numbers, use SimpleDateFormat so that it can be identified. ** " yyyy / MM / dd HH: mm: ss " ** is displayed in the format.

test.java

import java.io.File;
import java.text.SimpleDateFormat;

public class test{

  public static void main(String[] args){

    String filepath = "C:/tedkuma/BOX/20180729.csv";             //Referenced directory
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");//Date time format definition
    File targetFile = new File(filepath);
    Long lastModified = targetFile.lastModified();   //LastModified to get the modified date()use.
    String update_time = simpleDateFormat.format(lastModified);  //Format the value that came in long with simpleDateFormat
    System.out.println(update_time);
  }
}

Let's run it. I was able to get the update date and time.

** Try to combine with the process of exporting the file name **

Use the previously written Check the contents of the directory to write out the names and modification dates of multiple files.

test.java

import java.io.File;
import java.text.SimpleDateFormat;

public class test
{
    public static void main(String[] args)
    {
        String filepath = "C:/tedkuma/BOX/";

        File dir = new File(filepath);
        File[] list = dir.listFiles();          //Get a list of files using listFiles
        for(int i=0; i<list.length; i++) {
          String filename = list[i].getName();
          SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");//Date time format definition
          File targetFile = new File(filepath+filename);
          Long lastModified = targetFile.lastModified();
          String update_time = simpleDateFormat.format(lastModified);
          System.out.println(update_time+"："+filename);
        }
    }
}

Let's run it. The file name and update date could be displayed.

** Calculate time **

Use the Calendar class to calculate the time. (Added import java.util.Calendar;) You can get the current time with ** Calendar.getInstance () **. With the variable .add (Calendar.DATE, 1) ;, the time after 1 day, if you change the DATE to MINUTE, after 1 minute, You can also get the time one day ago or one minute ago by changing the second argument 1 to -1.

Since the lastModified (long type) that got the update date cannot be directly converted to the Calendar type I am using a Date type that can be converted to either. (Added import java.util.Date;)

You can use ** compareTo () to compare the size **. When you write ** A . CompareTo ( B **) ** A > ** B ** When A is in front, -1 ** A ** < B ** When A is later, 1 ** A ** = ** B ** At the same time, 0 is returned.

** Identify files that have been updated within 1 day from updated files **

I don't want to get the updated files that are updated every second I put in the if condition that the update time is within 1 day and 10 minutes or more have passed.

test.java

import java.io.File;
import java.util.Date;
import java.util.Calendar;
import java.text.SimpleDateFormat;

public class test{

    public static void main(String[] args){
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        String filepath = "C:/tedkuma/BOX/";

        File dir = new File(filepath);
        File[] list = dir.listFiles();

        Calendar st = Calendar.getInstance();//Get the current date and time with the Calendar class
        st.add(Calendar.DATE, -1);           //Get 1 day ago
        Date start = st.getTime();           //Change to Date

        Calendar en = Calendar.getInstance();//Get the current date and time with the Calendar class
        en.add(Calendar.MINUTE, -10);        //Get 10 minutes ago
        Date end = en.getTime();

        for(int i=0; i<list.length; i++) {  //Execute processing for files in the target path
          String filename = list[i].getName();
          File targetFile = new File(filepath+filename);
          Long lastModified = targetFile.lastModified();
          Date koushin = new Date(lastModified);

          if(start.compareTo(koushin)<0 && end.compareTo(koushin)>0){//Compare with compareTo
            String update_time = simpleDateFormat.format(koushin);
            System.out.println(update_time+"："+filename);
          }
        }
    }
}

Let's run it. Except for the file being updated, the files within 1 day of the update could be obtained.