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Java获取当前时间

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

public class Datetest {
//    SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd 20:00:00");
    public static void main(String[] args) {
        //SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd 00:00:00");
        //SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:MM:ss");
        Date date = new Date();
        //String time = simpleDateFormat.format(date);
        System.out.print(date);
        System.out.print(time


    }

}

1. SimpleDateFormat指定时间格式 2017-08-05 14:08:00，2017-08-05 20:00:00

2. System.out.print(date);直接输出当前时间，格式Sat Aug 05 14:05:31 CST 2017

 Calendar currentDate = new GregorianCalendar();
        currentDate.set(Calendar.HOUR_OF_DAY, 0);
        currentDate.set(Calendar.MINUTE, 0);
        currentDate.set(Calendar.SECOND, 0);
        String startTime = simpleDateFormat.format(currentDate.getTime());

1.2017-08-05 00:00:00 第二种方式输出每天的开始时间。