Java——时间和日期处理

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Date

Date date = new Date();

获取时间

        Date d = new Date();
//      Date d2=new Date(System.currentTimeMillis()-24*60*60*1000);
        System.out.println(d);
//      System.out.println(System.currentTimeMillis());

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Calender

• SimpleDateFormat：规范日期格式
  
  

设置当前基准时间

        Date d = new Date();

        //Calendar
        Calendar cal = Calendar.getInstance();
        //设置当前基准时间
        cal.setTime(d);
        // set：field设置的时间属性,value是设置的值
        //cal.set(Calendar.DATE, 19);

    // add方法:增加或减少时间值
    cal.add(Calendar.DATE, 2);
    //System.out.println(cal.getTime());

格式化时间

        SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
        System.out.println(format.format(cal.getTime()));

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计算两个年份之间的闰年数量

public static boolean isLeapYear(int year){
          return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) ;
         }

    public static void main(String[] args) {
        Date d = new Date();
        Calendar cal = Calendar.getInstance();
        cal.setTime(d);
        SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日");
        System.out.println(format.format(cal.getTime()));
        System.out.println("=======40天后取写真========");
        cal.add(Calendar.DATE, 40);
        System.out.println(format.format(cal.getTime()));
        System.out.println("======闰年个数========");
        int count=0;
        for(int i=1970;i<2011;i++){
            if(isLeapYear(i)){
                System.out.println(i+"是闰年");
                count++;
            }
        }
        System.out.println("闰年数量："+count);

    }

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时间和日期处理的综合练习

public static void sub(){
        System.out.println("两个日期为：2014-3-8和2017-8-17");
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        format.setLenient(false);
        try {
            Date date1= format.parse("2014-3-8");
            Date date = format.parse("2017-8-17");
            long day =(date.getTime()-date1.getTime())/(1000*60*60*24);
            System.out.println("相差天数："+day);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    //毫秒转日期
    public static void change(){
        Scanner sc= new Scanner(System.in);
        Date date = new Date();
//      Long time = date.getTime();
//      System.out.println("当前日期的毫秒数："+time);
        System.out.println("请输入一个毫秒数：");
        Long time = sc.nextLong();
        Date d = new Date(time);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println("转换成日期:"+sdf.format(d));
    }

    public static void today(){
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss");
        System.out.println("今天日期:"+sdf.format(date));
    }

    public static void subAdd(){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date = new Date();
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        System.out.println("当前的日期："+sdf.format(date));
        cal.add(Calendar.DATE, 10);
        System.out.println("加了10天后的日期："+sdf.format(cal.getTime()));
        cal.add(Calendar.DATE, -8);
        System.out.println("减去8天后的日期："+sdf.format(cal.getTime()));
    }

    public static void addSub(){
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        format.setLenient(false);
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入指定日期：");
        try {
            String str = sc.next();
            Date date1= format.parse(str);
            Calendar cal = Calendar.getInstance();
            cal.setTime(date1);
            cal.add(Calendar.DATE, 10);
            System.out.println("加了10天后的日期："+format.format(cal.getTime()));
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

//日期格式化
    public static void sdf(){
        SimpleDateFormat format = new SimpleDateFormat("北京时间：yy年MM月dd日，为您报时：HH:mm:ss");
        Date d = new Date();
        Calendar cal = Calendar.getInstance();
        cal.setTime(d);
        System.out.println(format.format(cal.getTime()));

    }

    public static void main(String[] args) {
        System.out.println("===========返回两个日期之间相差的天数================");
        sub();
        System.out.println("===========毫秒转日期================");
        change();
        System.out.println("===========返回今天的日期=============");
        today();
        System.out.println("===========返回当前日期加减后的日期=============");
        subAdd();
        System.out.println("===========返回指定日期的加减天数=============");
        addSub();
        System.out.println("===========日期格式化=============");
        sdf();
    }