[java] Current timestamp as filename in Java

I want to name new files created by my Java application with the current timestamp.

I need help with this. How do I name the new files created with the current timestamp? Which classes should I include?

try this one

String fileSuffix = new SimpleDateFormat("yyyyMMddHHmmss").format(new Date());

Date, SimpleDateFormat and whatever classes are required on the I/O side of things (there are many possibilities).

You can get the current timestamp appended with a file extension in the following way:

String fileName = new Date().getTime() + ".txt";

Improving the @Derek Springer post with fill length function:

public static String getFileWithDate(String fileName, String fileSaperator, String dateFormat) {
    String FileNamePrefix = fileName.substring(0, fileName.lastIndexOf(fileSaperator));
    String FileNameSuffix = fileName.substring(fileName.lastIndexOf(fileSaperator)+1, fileName.length());
    //System.out.println("File= Prefix~Suffix:"+FileNamePrefix +"~"+FileNameSuffix);
    
    String newFileName = new SimpleDateFormat("'"+FileNamePrefix+"_'"+dateFormat+"'"+fileSaperator+FileNameSuffix+"'").format(new Date());
    System.out.println("New File:"+newFileName);
    return newFileName;
}

Using the funciton and its Output:

String fileSaperator = ".", format = "yyyyMMMdd_HHmm";
getFileWithDate("Text1.txt", fileSaperator, format);
getFileWithDate("Text1.doc", fileSaperator, format);
getFileWithDate("Text1.txt.json", fileSaperator, format);

Output:

Old File:Text1.txt   New File:Text1_2020Nov11_1807.txt
Old File:Text1.doc   New File:Text1_2020Nov11_1807.doc
Old File:Text1.txt.json  New File:Text1.txt_2020Nov11_1807.json

Use SimpleDateFormat as aix suggested to format the current time into a string. You should use a format that does not include / characters etc. I would suggest something like yyyyMMddhhmm

You can use DateTime

import org.joda.time.DateTime

Option 1 : with yyyyMMddHHmmss

DateTime.now().toString("yyyyMMddHHmmss")

Will give 20190205214430

Option 2 : yyyy-dd-M--HH-mm-ss

   DateTime.now().toString("yyyy-dd-M--HH-mm-ss")

will give 2019-05-2--21-43-32