java获得之前的时间, 时间的减法运算实现

　　　　  
//方法一
　　 SimpleDateFormat sdf  = new SimpleDateFormat("yyyy-MM-dd");  
        String maxDateStr = "2018-01-01";  
        String minDateStr = "";  
        Calendar calc =Calendar.getInstance();  
        try {  
            calc.setTime(sdf.parse(maxDateStr));  
            calc.add(calc.DATE, -30);  
            Date minDate = calc.getTime();  
            minDateStr = sdf.format(minDate);  
            System.out.println("minDateStr:"+minDateStr);
        } catch (ParseException e1) {  
            e1.printStackTrace();  
        }  
 

//方法二:

　　 Calendar now = Calendar.getInstance();
        now.add(Calendar.DAY_OF_MONTH, -30);
        String endDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(now.getTime());
        System.out.println(endDate);
 

//方法三：

　　　　 
		//java8 新特性
        LocalDateTime now = LocalDateTime.now();
        now = now.minus(30, ChronoUnit.DAYS);
        System.out.println(now.toString());
 

 

//方法四：

        import org.apache.commons.lang3.time.DateUtils;

        Date now = new Date();
        Date startDate = DateUtils.addDays(now, -30);
 

//方法五：

       SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
       Calendar c = Calendar.getInstance();
         
        //过去七天
        c.setTime(new Date());
        c.add(Calendar.DATE, - 7);
        Date d = c.getTime();
        String day = format.format(d);
        System.out.println("过去七天："+day);
         
        //过去一月
        c.setTime(new Date());
        c.add(Calendar.MONTH, -1);
        Date m = c.getTime();
        String mon = format.format(m);
        System.out.println("过去一个月："+mon);
         
        //过去三个月
        c.setTime(new Date());
        c.add(Calendar.MONTH, -3);
        Date m3 = c.getTime();
        String mon3 = format.format(m3);
        System.out.println("过去三个月："+mon3);
         
        //过去一年
        c.setTime(new Date());
        c.add(Calendar.YEAR, -1);
        Date y = c.getTime();
        String year = format.format(y);
        System.out.println("过去一年："+year);