java.lang.illegalargumentexception at java.base/java.util.Date.parse

/**
 * @author lautturi.com 
 * Java example: parse unix timestamp string to date
 */

import java.text.SimpleDateFormat;
import java.util.*;

public class Lautturi {

	public static void main(String[] args) {
		String timeStamp = "1521635000000";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String sd = sdf.format(new Date(timeStamp));
		System.out.println(sd);
	}
}

output:

Exception in thread "main" java.lang.IllegalArgumentException
	at java.base/java.util.Date.parse(Date.java:612)

IllegalArgumentException:
The Date expected a long type.

public class Lautturi {
	public static void main(String[] args) {
		String timeStamp = "1521635000000";
		long l=Long.parseLong(timeStamp);
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String sd = sdf.format(new Date(l));
		System.out.println(sd);
	}
}