java 时间操作

public class DateCa {
    
    public static void main(String[] args) throws ParseException {
        
        /** 时间操作首推Calendar 格里高利历 **/
        Calendar ca =  Calendar.getInstance();
        //获取日期的单个属性:年,月,周,日,时,分
        System.out.println(ca.get(Calendar.YEAR));
        System.out.println(ca.get(Calendar.MONTH));//获取月份从0开始
        System.out.println(ca.get(Calendar.WEEK_OF_YEAR));
        System.out.println(ca.get(Calendar.DAY_OF_MONTH));
        System.out.println(ca.get(Calendar.HOUR_OF_DAY));
        System.out.println(ca.get(Calendar.MINUTE));

        //日期操作
        ca.add(Calendar.YEAR, 2);//退后两年
        System.out.println(ca.get(Calendar.YEAR));
        ca.add(Calendar.MONTH, 2);//退后两月
        System.out.println(ca.get(Calendar.MONTH));
        ca.add(Calendar.DAY_OF_MONTH, 10);//退后两天
        System.out.println(ca.get(Calendar.DAY_OF_MONTH));
        
        //直接设置所需时间
        ca.set(Calendar.YEAR,100);//将给定的日历字段设置为给定值。
        System.out.println(ca.get(Calendar.YEAR));
        ca.set(2018, 7, 12);
        System.out.println(ca.get(Calendar.YEAR));
        System.out.println(ca.get(Calendar.MONTH));
        System.out.println(ca.get(Calendar.DAY_OF_MONTH));
        
        //时间比较推荐
        System.out.println(ca.after(new Date()));
        System.out.println(ca.before(new Date()));

        //也可以获取指定时区的时间系统
        System.out.println(Calendar.getInstance(Locale.ENGLISH));
        
        /** 其他时间操作**/
        //当前秒数
        System.out.println(System.currentTimeMillis());
        System.out.println(new Date().getTime());
        //时间格式化
        SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        System.out.println(sf.format(ca.getTime()));
        System.out.println(sf.parse("2018-10-12 09:18:23").after(new Date()));
    }
}