Java基础 ----常用时间类

Java基础 ----常用时间类

• java.util.Date
• java.util.Calendar
• java.text.SimpleDateFormat

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new Date().getTime() && System.currenTimeMillis()

	Date date = new Date();
	System.out.println(date);//新建date默认取现在时间
	long dateTime = date.getTime();
	System.out.println(dateTime);//long型毫秒

    /*********Date<>System.currentTimeMillis关系转换***********/
    long currentTime = System.currentTimeMillis();
    System.out.println(currentTime);
    Date currentDate = new Date(currentTime);
    System.out.println(currentDate);

Output:

Calendar && Date

	Calendar calendar = Calendar.getInstance(); System.out.println(calendar.getTime());
    calendar.set(Calendar.MONTH, 0);    System.out.println(calendar.getTime());//Calendar常用set方法,可设置年月日,时分秒
    calendar.add(Calendar.MONTH, 1);    System.out.println(calendar.getTime());//Calendar常用add方法可添加年月日,时分秒,数值可负数
    Date calendarDate = calendar.getTime(); System.out.println(calendarDate);//Calendar转Date
    calendar.setTime(calendarDate); System.out.println(calendar.getTime());//Date转Calendar

Output:

SimpleDateFormat

	SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
    Date date = new Date();
    System.out.println(date);
    String formatDateString = simpleDateFormat.format(date);//Date转String
    System.out.println(formatDateString);
    try {
        Date parseDate = simpleDateFormat.parse("2018-10-01");//String转Date
        System.out.println(parseDate);
    }catch (ParseException pe){
        pe.getStackTrace();
    }

Output: