import org.testng.annotations.Test;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class TestDate {

    @Test
    public void test01() throws ParseException {

        Date dt= new Date();
        long s=System.currentTimeMillis();
        long long1= 1533954986837L;
        SimpleDateFormat dtf = new SimpleDateFormat("yyyy-MM-dd");
        SimpleDateFormat dtf1 = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss@SSS");
        String sdate =dtf1.format(long1);
        System.out.println(sdate);

        System.out.println(dtf.format(dt));
        System.out.println(dtf1.format(dt));
        System.out.println(dtf1.format(dt).toString());


        // Date -> String
        Date date = new Date(System.currentTimeMillis());
        System.out.println(dtf.format(date));

        // String -> Date
        String timeString = "2018-08-11 11:44:27";
        Date newDate = dtf.parse(timeString);
        System.out.println(newDate);

    }

}

Java 中時間處理 System.currentTimeMillis()