配合下面的案例可以更加深度的了解
需要导包java.util.Date
Date d = new Date(); //两种都是获取到现在时间的时间戳 long t1 = d.getTime();//这里返回的是long类型的时间戳 long t2 = System.currentTimeMillis();//同样返回的是long类型的时间戳 Date d3 =new Date(t2);//将long类型转成Date
需要导包java.util.Calendar
Calendar c = Calendar.getInstance(); c.set(2021, 5 - 1, 18);//这里返回的是Date int year = c.get(1); System.out.println(year); int month = c.get(Calendar.MONTH) + 1;//0代表一月,以此类推应当加一 System.out.println(month); int day = c.get(Calendar.DAY_OF_MONTH);//当月中的第几天 System.out.println(day); int hh = c.get(Calendar.HOUR);//12小时 hh = c.get(Calendar.HOUR_OF_DAY);//24小时 System.out.println(hh); int mm = c.get(Calendar.MINUTE); System.out.println(mm); int ss = c.get(Calendar.SECOND); System.out.println(ss); int wk = c.get(Calendar.DAY_OF_WEEK); //1 星期日 2 星期一 3星期二 4 星期三 5 星期四 6星期五 7星期六 //System.out.println(wk);
需要导包java.text.SimpleDateFormat
Date d = new Date(); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");//定义格式 System.out.println(sdf.format(d));//初始化date System.out.println(d.getTime()); //返回一个时间戳 Date birth = sdf.parse("2001-7-20 0:0:0");定义一个时间点
import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class Date01 { public static void main(String[] args) { Date d = new Date(); //时间戳 long 数字 long t1 = d.getTime(); long t2 = System.currentTimeMillis(); //将long转成Date Date d3 = new Date(t2); Calendar c = Calendar.getInstance(); c.set(2021, 5 - 1, 18); //将Calendar 日历类实例,转成Date Date d2 = c.getTime(); SimpleDateFormat s = new SimpleDateFormat("yyyy年MM月dd日"); System.out.println(s.format(d)); System.out.println(s.format(d2)); } }
public class Date02 { public static void main(String[] args) throws ParseException { //使用Date 导入并实例化,java.util.Date Date d = new Date(); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); System.out.println(sdf.format(d)); System.out.println(d.getTime()); //返回一个时间戳 long now = d.getTime() + (1000 * 60 * 60 * 24 * 10); d.setTime(now); System.out.println(sdf.format(d)); //计算两个日期之间相关的天数 Date birth = sdf.parse("2001-7-20 0:0:0"); //将字符串解析转换为Date Date ddd = new Date(); long days = (ddd.getTime() - birth.getTime())/1000/60/60/24; System.out.println(days); } }
public class Date03 { public static void main(String[] args) throws ParseException { Locale.setDefault(Locale.US); Calendar c = Calendar.getInstance(); c.set(2021, 7 - 1, 27); //year int year = c.get(1); System.out.println(year); int month = c.get(Calendar.MONTH) + 1; System.out.println(month); int day = c.get(Calendar.DAY_OF_MONTH); System.out.println(day); int hh = c.get(Calendar.HOUR);//12小时 hh = c.get(Calendar.HOUR_OF_DAY);//24小时 System.out.println(hh); int mm = c.get(Calendar.MINUTE); System.out.println(mm); int ss = c.get(Calendar.SECOND); System.out.println(ss); int wk = c.get(Calendar.DAY_OF_WEEK); //1 星期日 2 星期一 3星期二 4 星期三 5 星期四 6星期五 7星期六 //System.out.println(wk); if (wk == 1) { System.out.println("今日是星期日"); } else if (wk == 2) { System.out.println("今日是星期一"); } else if (wk == 3) { System.out.println("今日是星期二"); } else if (wk == 4) { System.out.println("今日是星期三"); } else if (wk == 5) { System.out.println("今日是星期四"); } else if (wk == 6) { System.out.println("今日是星期五"); } else { System.out.println("今日是星期六"); } Locale.setDefault(Locale.CHINA); System.out.printf("%tA%n",c); Date d = new Date(); //0 星期日 1 星期一 6 星期六 int ww = d.getDay(); System.out.println(ww); } }