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This article introduces the relevant knowledge of "how to format the input date and time of Java". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Request:

Use DateTimeFormatter to achieve: use the scanner to get the input time (year, month, day and hour), the format of this time is the commonly used format, and then format the time, output the formatted time to the console, you can repeatedly enter the time in the console. The formatted time refers to the display time of WeCom's chat record.

Analysis:

1. The common format of time is:

Xxxx-xx-xx xx:xxxxxx/xx/xx xx:xxxxxx.xx.xx xx:xx and other formats

two。 The explicit time format of Wechat is:

Explicit today: 00:01-23:59; yesterday explicit: 01:01 yesterday; the day before yesterday explicit: 02:02 the day forward all week explicit: what day 02:02; time further pushed forward only shows: a few days at 02:02 different years are explicit: a few years, days at 02:02 can also consider writing a tomorrow explicit: tomorrow 02 display 02 the rest of the time explicit: what day of the month 02 02

3. Consider the date under special circumstances:

For example, if the current day is the 1st, then the last day of last month was yesterday and pushed forward one week, it is explicit: what day is 02:02? if the current day is not greater than the 7th, then push forward one week to last month, you should also consider converting it to a week.

4. Enter a time first, and then use DateTimeFormatter to format that time

For example, enter: 2020-1-11 12:22 and format the result as: 12:22

Code implementation

The program begins:

Package hrkj.chapter7.dateTimeFormatter.Test1;/** * Program start entry

* 7:10:04 on January 9, 2020 * * @ author wcf * @ version 1.0 * / public class Test {/ * Program entry * * @ param args entry Parameter * / public static void main (String [] args) {/ / the program starts running DateTimeFormatterTest.inoutDateTime ();}}

Regular expressions that need to be used, such as date, time, etc.

Regular expression of package hrkj.chapter7.dateTimeFormatter.Test1;/** * date and time

* 7:25:11 on January 9, 2020 * * @ author wcf * @ version 1.0 * / public enum Regex {/ * matches the leap year * / LEEP_YEAR ("((\ d {2} (0 [48] | [2468] [048] | [13579] [26])) | ((0 [48] | [2468] [048] | [13579] [26]) 00)] [-\ /\. / * match normal year * / COMMON_YEAR ("(\\ d {3} [1-9] |\\ d {2} [1-9]\\ d |\ d [1-9]\\ d {2} | [1-9]\\ d {3}) [-\ /\\.] (0? [13578] | 1 [02]) [-\ /\.] (0? [1-9]) [0? [1-9] | [12]\ d | 3 [01] ]) | ((0? [469] | 11) [-\ /\.] (0? [1-9] | [12]\\ d | 30)) | (03,2 [-\ /\.] (0? [1-9] | 1\\ d | 2 [0-8])) ") / * matching time * / TIME ("([01]?\\ d | 2 [0-3]): [0-5]?\\ d"), / * * exit program * / EXIT ("exit | exit") / * regular * / private final String str; / * Parametric constructor * * @ param string regular * / private Regex (String string) {this.str = string;} / * * get regular * * @ return regular * / public String getStr () {return str;}}

Prompt message:

Package hrkj.chapter7.dateTimeFormatter.Test1;/** * prompt message

* 7:25:53 on January 9, 2020 * * @ author wcf * @ version 1.0 * / public enum Hint {/ * Please enter date time * / INPUT_DATE_TIME ("Please enter date time:"), / * * date time format * / DATETIMEFORMAT ("Common format: xxxx-xx-xx xx:xx\ n\ t xxxx/xx/xx xx:xx\ n\ t xxxx.xx.xx xx:xx") / * date error * / INVOKE_DATE ("date error"), / * * time error * / INVOKE_TIME ("time error"), / * * date time error * / INVOKE_DATE_TIME ("wrong date and time!"), / * * continue or exit * / CONTINUE_OR_QUIT ("exit: program exit\ nPlease enter:") / * * Program ends * / END_OF_PROGRAM ("exit succeeded, program ends!") / * * hint * / private final String str; / * there is a parameter constructor * * @ param str hint * / private Hint (String str) {this.str = str;} / * get prompt * / public void println () {System.out.println (str);}}

Template string formatted by date and time:

Package hrkj.chapter7.dateTimeFormatter.Test1;/** * template string formatted by date and time

* 7:17:19 on March 1, 2019 * * @ author wcf * @ version 1.0 * / public enum Pattern {/ * morning and afternoon * / TIME ("a HH:mm"), / * * yesterday * / YESTERDAY ("yesterday HH:mm"), / * * tomorrow * / TOMORROW ("tomorrow HH:mm") / * hours of the week * / WEEK_TIME ("E HH:mm"), / * * hours of the month * / MONTH_DAY_TIME ("HH:mm of the day of M month"), / * * hours of the day of the year * / YEAR_MONTH_DAY_TIME ("HH:mm of the day of the month of the year") / * * explicit mode * / private final String str; / * has parameter constructor * * @ param str mode * / private Pattern (String str) {this.str = str;} / * get explicit mode * * @ return explicit mode * / public String getStr () {return str;}}

Enter a date and time for processing:

Package hrkj.chapter7.dateTimeFormatter.Test1;import java.util.Scanner;/** * enter date and time for processing

* 7:09:31 on January 9, 2020 * * @ author wcf * @ version 1.0 * / public class DateTimeFormatterTest {/ * * Leap year regular * / private final static String LEEP_YEAR = Regex.LEEP_YEAR.getStr (); / * * regular year regular * / private final static String COMMON_YEAR = Regex.COMMON_YEAR.getStr (); / * * time regular * / private final static String TIME = Regex.TIME.getStr () / * * exit regular * / private final static String EXIT = Regex.EXIT.getStr (); / * * static initialization block * / static {/ / enter prompt Hint.INPUT_DATE_TIME.println (); / / date-time format Hint.DATETIMEFORMAT.println (); / / exit instruction Hint.CONTINUE_OR_QUIT.println () } / * Private constructor * / private DateTimeFormatterTest () {/ / Private constructor / / unable to create an instance of this class} / * enter date and time * / public static void inoutDateTime () {/ / Scanner Scanner scanner = new Scanner (System.in) / / scan console input while (scanner.hasNextLine ()) {/ / receive console input and remove the spaces before and after input String str = scanner.nextLine (). Trim (); / / A pair of input characters to judge if (str.matches (EXIT)) {/ / program exit Hint.END_OF_PROGRAM.println (); / / close scanner scanner.close (); / / exit virtual machine System.exit (0) / / judge flat leap year} else if (str.matches (LEEP_YEAR + TIME) | | str.matches (COMMON_YEAR + TIME)) {/ / A pair of entered date-time strings are formatted DateTimeFormatterTools.format (str); / / prompt Hint.CONTINUE_OR_QUIT.println () after formatting;} else {/ / the date and time entered is incorrect Hint.INVOKE_DATE_TIME.println () / / enter prompt Hint.INPUT_DATE_TIME.println (); continue;}}

Process the date and time entered:

Package hrkj.chapter7.dateTimeFormatter.Test1;import java.time.LocalDateTime;import java.time.MonthDay;import java.time.Year;import java.time.format.DateTimeFormatter;import java.util.Arrays;/** * processes the date and time entered

* 8:08:45 on January 9, 2020 * * @ author wcf * @ version 1.0 * / public class DateTimeFormatterTools {/ * * the day of the month * / private static final String YEAR_MONTH_DAY_TIME = Pattern.YEAR_MONTH_DAY_TIME.getStr (); / * * the day of the month * / private static final String MONTH_DAY_TIME = Pattern.MONTH_DAY_TIME.getStr () / * week hours * / private static final String WEEK_TIME = Pattern.WEEK_TIME.getStr (); / * * morning and afternoon hours * / private static final String TIME = Pattern.TIME.getStr (); / * * yesterday hours * / private static final String YESTERDAY = Pattern.YESTERDAY.getStr (); / * * tomorrow hours * / private static final String TOMORROW = Pattern.TOMORROW.getStr () / * current year * / private static int currentYear = Year.now (). GetValue (); / * * current month * / private static int currentMonth = MonthDay.now (). GetMonthValue (); / * * current day * / private static int currentDay = MonthDay.now (). GetDayOfMonth (); / * * Big Moon * / private static int [] bigMonth = {1, 3, 5, 7, 8, 10, 12} / * * Xiaoyue * / private static int [] smallMonth = {4,6,9,11} / * Private constructor * / private DateTimeFormatterTools () {/ / Private constructor, unable to instantiate} / * process entered date time * * @ param str entered date time * / public static void format (String str) {/ / split date and time with spaces String [] datetime = str.split (""); / / split date String date = datetime [0] / / split time String time = datetime [1]; / / date segmentation method String splitter = ""; / / date can be used -. / to segment / / if one of the three is included, then use these to segment if (date.contains (".") {splitter = "\\.";} else if (date.contains ("-")) {splitter = "-";} else if (date.contains ("/")) {splitter = "/" } / / use date segmentation method to segment date String [] dateString = date.split (splitter); / / use: split time, time can only be: split String [] timeString = time.split (":") / / the array length after time division is not 2, because the time entered is only sometimes and if (timeString.length! = 2) {/ / time error Hint.INVOKE_TIME.println (); return;} / / the array length after date division is not 3 error, because the date entered must have year, month and day if (dateString.length! = 3) {/ / date error Hint.INVOKE_DATE.println () Return;} / / enter annual int year = Integer.valueOf (dateString [0]); / / enter monthly int month = Integer.valueOf (dateString [1]); / / enter daily int day = Integer.valueOf (dateString [2]); / / enter int hour = Integer.valueOf (timeString [0]); / / enter sub-int minute = Integer.valueOf (timeString [1]) / / A reassemble String str1 = year + splitter + month + splitter + day + "" + hour + ":" + minute; / / A pair of combined strings to parse DateTimeFormatter ofPattern = DateTimeFormatter.ofPattern ("y" + splitter + "M" + splitter + "d" + "Hpurm"); / / parse the string into a date-time object LocalDateTime parse = LocalDateTime.parse (str1, ofPattern) / / same year if (year = = currentYear) {/ / same month if (month = = currentMonth) {/ / same day if (day = = currentDay) {/ / Today printDateTime (TIME, parse);} else if (day-currentDay = = 1) {/ / tomorrow printDateTime (TOMORROW, parse);} else if (day-currentDay = =-1) {/ / yesterday printDateTime (YESTERDAY, parse) } else if (day-currentDay > =-7 & & day-currentDay = 0 & & currentDay = = 31) {/ / tomorrow printDateTime (TOMORROW, parse); return;} else if (Arrays.binarySearch (smallMonth, currentMonth) > = 0 & & currentDay = = 30) {/ / tomorrow printDateTime (TOMORROW, parse); return } else if (currentMonth = = 2) {/ / determine whether a leap year or an ordinary year if ((year% 4 = = 0 & & year% 100! = 0) | | year% 400 = = 0) {if (currentDay = = 29) {/ / tomorrow printDateTime (TOMORROW, parse); return;}} else {if (currentDay = = 28) {/ / tomorrow printDateTime (TOMORROW, parse); return } else {/ / use the day of the month to output printDateTime (MONTH_DAY_TIME, parse);}} else {/ / the input date is not 1, which outputs the day of the month printDateTime (MONTH_DAY_TIME, parse) } / / previous month} else if (month-currentMonth = =-1) {/ / if the current day is 1, determine whether the input date is the last day of the previous month if (currentDay = = 1) {/ / determine whether it is a big month, a small month or February, and whether the number of days entered is the last day of the month, yes, yesterday if (Arrays.binarySearch (bigMonth, month) > = 0 & day = 31) {/ / yesterday printDateTime (YESTERDAY, parse); } else if (Arrays.binarySearch (smallMonth, month) > = 0 & & day = = 30) {/ / yesterday printDateTime (YESTERDAY, parse); return;} else if (month = = 2) {/ / determine whether it is a leap year or an ordinary year if ((year% 4 = = 0 & & year% 100! = 0) | | year% 400 = = 0) {if (day = 29) {/ / yesterday printDateTime (YESTERDAY, parse); }} else {if (day = = 28) {/ / yesterday printDateTime (YESTERDAY, parse); return;} / / if the current day is not less than 7, enter the month day time, and if less than 7, convert from the current day to the previous week to week if (currentDay > = 7) {/ / output month day time printDateTime (MONTH_DAY_TIME, parse) / / if the current day is less than 7, the current day is converted to week} else if (Arrays.binarySearch (bigMonth, month) > = 0 & & 31-day + currentDay.

= 0 & & 30-day + currentDay < 7) {/ / convert month / day to week printDateTime (WEEK_TIME, parse);} else if (month = = 2) {/ / judge whether it is leap year or plain year if ((year% 4 = = 0 & & year% 100! = 0) | | year% 400 = = 0) {if (29-day + currentDay < 7) {/ year month day convert to week printDateTime (WEEK_TIME, parse) } else {/ / if forward exceeds one week output month day printDateTime (MONTH_DAY_TIME, parse);}} else {if (28-day + currentDay < 7) {/ / year month day conversion to week printDateTime (WEEK_TIME, parse);} else {/ / if forward exceeds one week output month day hour printDateTime (MONTH_DAY_TIME, parse) } else {/ / current day forward exceeds one week output month day hour printDateTime (MONTH_DAY_TIME, parse);} else {/ / different month, output month day hour printDateTime (MONTH_DAY_TIME, parse);} else {/ / different year, output year month day hour printDateTime (YEAR_MONTH_DAY_TIME, parse) }} / * format result * * @ param pattern pattern string * @ param datetime time * / private static void printDateTime (String pattern, LocalDateTime datetime) {/ / format time through pattern string DateTimeFormatter ofPattern = DateTimeFormatter.ofPattern (pattern); / / print formatted time System.out.println ("format result:\ n\ t" + ofPattern.format (datetime));}}

Code test results:

Please enter date time: common format: xxxx-xx-xx xx:xxxxxx / xx/xx xx:xxxxxx.xx.xx xx:xxexit: program exited Please enter: 2020-1-11 12:22 format result: afternoon 12:22exit: program exit Please enter: 2020-1-11 2:22 format result: morning 02:22exit: program exit Please enter: 2020-1-10 1:22 format result: yesterday 01:22exit : program exiting Please enter: 2020-1-7 12:22 formatting result: Tuesday 12:22exit: program exiting Please enter: 2020-1-12 12:22 formatting result: tomorrow 12:22exit: program exiting Please enter: 2020-1-13 12:22 formatting result: Jan 13 12:22exit: program exiting Please enter: 2020-2-22 12:22 formatting result: Feb. 22 12:22exit: program withdrawal Please enter: 2019-12-31 12:22 format result: December 31, 2019 12:22exit: program exit please enter:

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