Java 日期时间获取和显示

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;public class Main { public static void main(String[] args) {
Calendar calendar = Calendar.getInstance(TimeZone.getDefault());
// FAQ :
// 1.不同地区国家时间格式显示和同步问题？ UTC,格林威治？夏威夷？国际化 ~ locale
// 2.本地client和服务器时间同步问题，比如定时下发执行任务，本地预定时早于服务器当前时间，则无法执行
System.out.println("\nTimezone: " + TimeZone.getDefault()); long time = calendar.getTimeInMillis();
Date date1 = calendar.getTime();
Date date2 = new Date(); // get current date // method1: direct format fun call
// a ~ AM/PM, 上午/下午
SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm"); // HH ~ 24小时制
System.out.printf("\nTime1 in 24h : " + sdf1.format(calendar.getTime())); SimpleDateFormat sdf11 = new SimpleDateFormat("yyyy-MM-dd hh:mm"); // hh ~ 12小时制
System.out.printf("\nTime11 in 12h : " + sdf11.format(calendar.getTime())); SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd a HH:mm", Locale.ENGLISH);
System.out.printf("\nTime2: " + sdf2.format(calendar.getTime())); SimpleDateFormat sdf3 = new SimpleDateFormat("yyyy年MM月dd日HH:mm");
System.out.printf("\nTime3: " + sdf3.format(calendar.getTime())); SimpleDateFormat sdf4 = new SimpleDateFormat("yyyy年MM月dd日 a HH:mm");
System.out.printf("\nTime4: " + sdf4.format(calendar.getTime())); // method2: use self define format func
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH);
int day = calendar.get(Calendar.DAY_OF_MONTH);
int hour = calendar.get(Calendar.HOUR_OF_DAY);
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND); // 欧美国家一周的第一天是星期天，这在java api代码中是写死的，因此这里要自己手动做下判断
// Calendar中的星期一、二、三、四、五、六、日、DAY_OF_WEEK等都是以一个常量的形式存在的，
// 我们设置setFirstDayOfWeek()并不能改变这些常量的值
int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); // 获取当天是星期几
boolean isFirstSunday = (calendar.getFirstDayOfWeek() == Calendar.SUNDAY);
if (isFirstSunday) {
dayOfWeek -= 1;
if (dayOfWeek == 0) {
dayOfWeek = 7;
}
} int dayOfWeekInMonth = calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH); // 某月中第几周. 按这个月1号算,1号起就是第1周,8号起就是第2周
int weekOfMonth = calendar.get(Calendar.WEEK_OF_MONTH); // 该月的第几周
int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR); // 一年的第几天，从1号算起
System.out.println("\n" + getFormattedTime(year, month, day, hour, minute));
System.out.println("\ndayOfWeek: " + dayOfWeek + "\ndayOfWeekInMonth: " + dayOfWeekInMonth
+ "\ndayOfYear: " + dayOfYear);
} /**
* 格式化日期字符串，形如 xx年xx月xx日xx:xx:xx
* @param year
* @param month
* @param day
* @param hour
* @param minute
* @return String
*/
public static String getFormattedTime(int year, int month, int day, int hour, int minute) {
String yearStr = "";
String monthStr = "";
String dayStr = "";
String hourStr = "";
String minuteStr = "";
// year
if (year < 10) {
yearStr = "0" + year;
} else {
yearStr = String.valueOf(year);
}
// month
if (month < 10) {
monthStr = "0" + month;
} else {
monthStr = Integer.toString(month);
}
// day
if (day < 10) {
dayStr = "0" + day;
} else {
dayStr = Integer.toString(day);
}
// hour
if (hour < 10) {
hourStr = "0" + hour;
} else {
hourStr = Integer.toString(hour);
}
// minute
if (minute < 10) {
minuteStr = "0" + minute;
} else {
minuteStr = Integer.toString(minute);
}
return yearStr + "年" + monthStr + "月" + dayStr + "日" + hourStr + ":" + minuteStr;
}
}