Java 日期时间格式化穿越小时和月

import java.util.*;

public class Main {
   public static void main(String[] args) throws Exception {
      Date d1 = new Date();
      Calendar cl = Calendar. getInstance();

      cl.setTime(d1);
      System.out.println("today is "+ d1.toString());

      cl. roll(Calendar.MONTH, 100);
      System.out.println("date after a month will be " + cl.getTime().toString() );

      cl. roll(Calendar.HOUR, 70);
      System.out.println("date after 7 hrs will be "+ cl.getTime().toString() );
   }
}