java - Recompile with -Xlint:deprecation for details

Question

I need to know how to fix these error notes:

Note: Summer.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

Here is my code:

import java.util.Calendar;
import java.util.*;

class Summer
{
    public static void main(String[] args)
    {
        Date d1 = new Date();
        Date j21 = new Date(d1.getYear(), 6, 21);
        if(d1.before(j21)) {
            long diff = j21.getTime() - d1.getTime();
            diff = diff / (1000 * 60 * 60 * 24);
            System.out.println("There are " + diff + " days until June 21st" );
        }
        else {
            long diff = d1.getTime() - j21.getTime();
            diff = diff / (1000 * 60 * 60 * 24);
            diff = 365 - diff;
            System.out.println("There are " + diff + " days until June 21st" );
        }
    }
}

Answer 1

This is not an error; it's a warning message.

Your program would run as you wrote it.

The reason why the compiler is giving you this warning is because you have used a deprecated function call.

By "recompile with -Xlint", the compiler means to inform you that you need to recompile your program like this:

javac -Xlint abc.java 

If you do so, the compiler will tell you which methods are deprecated so you can remove your calls to them. (If some method is deprecated, it usually means that a better implementation is available and that you should use that instead of the deprecated method.)