Java日期date格式

1、获取当前日期时间

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

Date day=new Date();    
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
System.out.println(df.format(day));  

2、时间比较

SimpleDateFormat sdf =   new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss");
        SimpleDateFormat sxx =   new SimpleDateFormat( "HH:mm:ss");
        String d1="07:55:30";
        String d2="2018-02-02 07:55:31".substring(11, 19);
        String d3="2018-02-01 17:55:31";

        try {
            Date dx = sxx.parse(d1);

            Date date2 = sxx.parse(d2);
            Date date3 = sdf.parse(d3);


            if(dx.before(date2)){
                System.out.println("Yes");
            }
            else{
                System.out.println("No");
            }

        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }