Java获取时间操作时间

Date

    public static void main(String[] args) throws InterruptedException {
    
    
        java.util.Date date = new java.util.Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        System.out.println(sdf.format(date));
        TimeUnit.SECONDS.sleep(1);//秒
        java.util.Date date2 = new java.util.Date();
        if (date2.getTime()>date.getTime()){
    
    
            System.out.println("date2在date后面");
        }else {
    
    
            System.out.println("date2在date前面");
        }
    }

SystemTime

	public static final Integer ONE_MIN  =    60000 ;
    public static final Integer ONE_HOUR =  3600000 ;
    public static final Integer ONE_DAY  = 86400000 ;

    public static void main(String[] args) {
    
    

        long time = System.currentTimeMillis();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        System.out.println("当前时间： "+sdf.format(time));
        System.out.println("加1分钟： "+sdf.format(time+ONE_MIN));
        System.out.println("减去1天： "+sdf.format(time-ONE_DAY));
        System.out.println("当前时间： "+sdf.format(new Date(System.currentTimeMillis())));


        System.out.println("毫秒：" + System.currentTimeMillis());
        System.out.println(" 秒 ：" + System.currentTimeMillis() / 1000);
        System.out.println(" 分 ：" + System.currentTimeMillis() / 1000 / 60);
        System.out.println(" 时 ：" + System.currentTimeMillis() / 1000 / 60 / 60);
        System.out.println(" 天 ：" + System.currentTimeMillis() / 1000 / 60 / 60 / 24);
    }

LocalDateTime

		LocalDate localDate = LocalDate.now() ;
        LocalTime localTime = LocalTime.now() ;
        java.time.LocalDateTime localDateTime = java.time.LocalDateTime.now();
        System.out.println("当前日期 "+localDate);
        System.out.println("当前时间 "+localTime);
        System.out.println("日期时间 "+localDateTime);

        System.out.println("\t"+"自定义时间 "+java.time.LocalDateTime.of(2022, 7, 25, 8, 0, 0));

        System.out.println();
        System.out.println("(plus*)方法操作时间(加法) :");
        System.out.println("\t"+"减三年时间 "+java.time.LocalDateTime.now().plusYears(-3));
        System.out.println("\t"+"加一周时间 "+java.time.LocalDateTime.now().plusWeeks(1));
        System.out.println("\t"+"减五个小时 "+java.time.LocalDateTime.now().plusHours(-5));
        System.out.println("\t"+"加一周时间 "+LocalDate.now().plusWeeks(1));
        System.out.println("\t"+"减两个小时 "+LocalTime.now().plusHours(-2));

        System.out.println();
        System.out.println("(minus*)方法操作时间(减法) ：");
        System.out.println("\t"+"两天前：" + java.time.LocalDateTime.now().minusDays(2));
        System.out.println("\t"+"两周后：" + java.time.LocalDateTime.now().minusWeeks(-2));
        System.out.println("\t"+"一月前：" + java.time.LocalDateTime.now().minusMonths(1));


        System.out.println();
        System.out.println("格式化时间格式 ：");
        System.out.println("\t"+"日期时间 "+localDateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss")));
        System.out.println("\t"+"日期时间 "+localDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE));
        System.out.println("\t"+"日期时间 "+LocalDate.now()+" "+LocalTime.now());

Calendar

public static String getWeek(Integer pa){
    
    
        HashMap<Integer, String> map = new HashMap<>();
        map.put(1,"星期一");
        map.put(2,"星期二");
        map.put(3,"星期三");
        map.put(4,"星期四");
        map.put(5,"星期五");
        map.put(6,"星期六");
        map.put(0,"星期日");
        return map.get(pa);
    }



    public static void main(String[] args) {
    
    

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.sss");
        java.util.Calendar ca = java.util.Calendar.getInstance();
        System.out.println("当前时间： "+sdf.format(ca.getTime()));
        ca.add(java.util.Calendar.MINUTE, +1); //分钟
        System.out.println("加1分钟： "+sdf.format(ca.getTime()));
        ca.add(java.util.Calendar.HOUR, -1); //小时
        System.out.println("减1小时： "+sdf.format(ca.getTime()));
        ca.add(java.util.Calendar.DATE, +1);// 日期加1
        System.out.println("增加1天： "+sdf.format(ca.getTime()));

        /**
         *  星期是从  日 一 二 三 四 五 六 排序的
         *  对应的index是   0 1 2 3 4 5  6
         *  Calendar.DAY_OF_WEEK获得到的是 1 2 3 4 5 6 7
         *  所以需要减1
         */
        System.out.println();
        System.out.println("获取当前星期：");
        java.util.Calendar canow = java.util.Calendar.getInstance();
        int index=canow.get(java.util.Calendar.DAY_OF_WEEK);
        System.out.println("周几？ "+(index-1));
        System.out.println("周几？ "+getWeek(index-1));
        System.out.println(sdf.format(canow.getTime())+"  "+getWeek(canow.get(java.util.Calendar.DAY_OF_WEEK)-1));

    }