工具类:Date

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

public class TestSimpleDateFormat {
    public static void main(String[] args) throws ParseException {
        
        Date date = new Date();
        
        //指定时间的格式(yyyy:年,MM:月,dd:日,HH:时,mm:分,ss:秒)
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        System.out.println("当前时间(格式)："+sdf.format(date));
        System.out.println("--------------------");
        
        //将文本转换为日期
        String dateStr = "2016-06-10 16:47:19";
        Date date2 = sdf.parse(dateStr);
        System.out.println("Date时间："+date2);
        System.out.println("--------------------");
        
        //Calendar类
        Calendar calendar = Calendar.getInstance();
        int year = calendar.get(Calendar.YEAR)+1;//0表示1月份
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        int hour = calendar.get(Calendar.HOUR_OF_DAY);
        int minute = calendar.get(Calendar.MINUTE);
        int second = calendar.get(Calendar.SECOND);
        System.out.println("当前时间："+year+"-"+month+"-"+day+" "+hour+":"+minute+":"+second);
        System.out.println("当前毫秒数："+calendar.getTimeInMillis());
        Date date3 = calendar.getTime();
        System.out.println("Date时间："+date3);
        System.out.println("--------------------");
    }
}

输出结果：
当前时间(格式)：2016-06-10 17:02:54
--------------------
Date时间：Fri Jun 10 16:47:19 CST 2016
--------------------
当前时间：2017-5-10 17:2:54
当前毫秒数：1465549374419
Date时间：Fri Jun 10 17:02:54 CST 2016
--------------------