1、某个时间与当前系统时间相差几小时(包括0.5等小数点)
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm");
Date rwks = simpleDateFormat.parse(“2019-10-16 18:00”);
Date now = simpleDateFormat.parse(new Date().toLocaleString());
long diff = rwks.getTime() - now.getTime() ;
float hours = diff / (float)(1000 * 60 * 60);
2、取当前系统时间的日期格式：
Calendar dayc1 = new GregorianCalendar();
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
Date daystart = sdf.parse(new Date().toLocaleString());
dayc1.setTime(daystart);
1>取系统当天的日期：
int towd = dayc1.get(Calendar.DATE);
2>取系统当天加1天的日期
dayc1.add(Calendar.DAY_OF_YEAR, 1);
xcsj = sdf.format(dayc1.getTime());
3>取系统当天是周几
int w=dayc1.get(Calendar.DAY_OF_WEEK)-1; (此方法是从周日开始)
if(w==0) w=7;
4>取系统当天是第几周
int week1 = dayc1.get(Calendar.WEEK_OF_MONTH);
3、当前时间减30分钟、1小时、2小时
public String getxcsj(String kssj,String min){
String xcsj = "";
try {
SimpleDateFormat sim = new SimpleDateFormat("HH:mm");
Date rwkssjd = sim.parse(kssj);
if("0.5".equals(min)){
Date txTime = new Date(rwkssjd.getTime() - 30*60*1000);
xcsj = sim.format(txTime);
}else if("1".equals(min)){
Date txTime = new Date(rwkssjd.getTime() - 60*60*1000);
xcsj = sim.format(txTime);
}else if("2".equals(min)){
Date txTime = new Date(rwkssjd.getTime() - 2*60*60*1000);
xcsj = sim.format(txTime);
}
} catch (Exception e) {
log.error("获取下次提醒时间错误"+e.toString(), e);
}
return xcsj;
}