How to subtract X day from a Date object in Java?

To subtract a certain number of days from a Date object in Java, you can use the Calendar class. The Calendar class allows you to manipulate the date and time values of a Date object.

Here's an example of how you can subtract X days from a Date object using the Calendar class:

import java.util.Calendar;
import java.util.Date;

public class Main {
  public static void main(String[] args) {
    // create a Calendar object and set it to the current date and time
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(new Date());

    // subtract 10 days from the calendar
    calendar.add(Calendar.DAY_OF_MONTH, -10);

    // get the modified Date object
    Date date = calendar.getTime();

    // print the date
    System.out.println(date);
  }
}

This code creates a new Calendar object and sets it to the current date and time. It then subtracts 10 days from the calendar using the add method and the Calendar.DAY_OF_MONTH field. Finally, it gets the modified Date object using the getTime method and prints it to the console.

Note that the add method allows you to add or subtract a certain number of days, months, years, etc. from the calendar. You can use the various fields of the Calendar class (such as Calendar.DAY_OF_MONTH, Calendar.MONTH, Calendar.YEAR, etc.) to specify the unit of time that you want to add or subtract.