java push forward current implementation time h N

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 * @author shafei
 * @version 1.0
 * @date 10:40 2019/9/27
 * @fun
 */
public class GetDate {
    public static void main(String[] args) {
        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                .format(new Date()));
        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
                .format(dateRoll(new Date(), Calendar.HOUR, -1)));
    }

    public static Date dateRoll(Date date, int i, int d) {
        // 获取Calendar对象并以传进来的时间为准
        Calendar calendar = Calendar.getInstance();
        calendar.setTime (DATE); 
        // long time now fixed scroll, converts the assignment type Date 
        Calendar.add (I, D); 
        // re-assignment to type Date 
        DATE = calendar.getTime (); 
        return DATE; 
    } 

}