File Name Not Able to Change

I am looking a way for convert my old file to a new file after my program processed the file. The new file will contain current timestamp after it’s been processed.For example, my old file will test.txt, after it’s been processed, it’s will change to test2017-10-13.txt. I had searched the solution around internet but I’m still cant make it work. Here is my current source code

LocalDate now2 =; 
System.out.println("The current day is :" +now2);
File oldFile1 = new File("C:\Users\user\Desktop\test.txt");
File newFile1 = new File("C:\Users\user\Desktop\test"+now2+".txt");
boolean success = oldFile1.renameTo(newFile1);

This is my sample output

The current day is :2017-10-13

Do it a bug reported in java because I found this information online or do there have any method to do it without copy out the contents from older file and write it into new file ?