Java09-获取当前日期的3种方式

package doudou;

import java.util.Date;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;

public class test_date {
    public static void main(String[] args) {
        System.out.println("============方式一：Date==========================");
        Date a = new Date();
        int current_year = a.getYear() + 1900;
        int current_month = a.getMonth() + 1;
        System.out.println("当前年：" + current_year);
        System.out.println("当前月：" + current_month);// Expired 月份 从0开始
        System.out.println("当前日：" + a.getDate());// Expired 日
        System.out.println("当前日期及时间:  " + a.toString()); // 当前日期及时间
        System.out.println(a.getClass());// 通过对象a调用getClass()方法返回Class

        System.out.println("============方式二：SimpleDateFormat和DateTimeFormatter==========================");
        // 格式化时间（SimpleDateFormat和DateTimeFormatter)
        System.out.println("！！！！SimpleDateFormat：线程不安全！！！！");
        Date date = new Date();
        String strDateFormat = "yyyy-MM-dd HH:mm:ss";
        SimpleDateFormat sdf = new SimpleDateFormat("当前日期及时间：  " + strDateFormat);
        System.out.println(sdf.format(date));

        String strDateFormat1 = "yyyy-MM-dd";
        SimpleDateFormat sdf1 = new SimpleDateFormat("当前日期：  " + strDateFormat1);
        System.out.println(sdf1.format(date));

        String strDateFormat2 = "HH:mm:ss";
        SimpleDateFormat sdf2 = new SimpleDateFormat("当前时间：  " + strDateFormat2);
        System.out.println(sdf2.format(date));

        System.out.println("！！！！DateTimeFormatter-LocalDateTime：线程安全！！！！");
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss");
        System.out.println("当前日期及时间：     " + dtf.format(LocalDateTime.now()));
        
        LocalDate localDate = LocalDate.now();
        System.out.println("当前日期：" + localDate.toString());
        LocalTime localTime = LocalTime.now().withNano(0);//去掉毫秒
        System.out.println("当前时间：" +localTime.toString());

        System.out.println("==============方式三：Calendar====================");
        Calendar cal = Calendar.getInstance();
        Date a1 = cal.getTime();
        System.out.println("当前日期及时间:" + a1);
        int day = cal.get(Calendar.DATE);
        int month = cal.get(Calendar.MONTH) + 1;
        int year = cal.get(Calendar.YEAR);
        int hour = cal.get(Calendar.HOUR);
        int minute = cal.get(Calendar.MINUTE);
        int second = cal.get(Calendar.SECOND);
        System.out.println("Month:" + month);
        System.out.println("Day:" + day);
        System.out.println("year:" + year);
        System.out.println("WEEK_OF_YEAR：" + cal.get(cal.WEEK_OF_YEAR));
        System.out.println("WEEK_OF_MONTH：" + cal.get(cal.WEEK_OF_MONTH));
        System.out.println("DAY_OF_WEEK:" + cal.get(cal.DAY_OF_WEEK));// 从周日开始算
        System.out.println("现在是" + year + "年" + month + "月" + day + "日");
        System.out.println("现在是" + hour + "时" + minute + "分" + second + "秒");
    }

}