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Java String to date parsing error, how to do it properly

I am interested to know if my code is correct and it doesn't have any issues. Date is taken from binary file, written as a string in such format YYYY-MM-DD/Hours-minutes-seconds example: 2022-01-23/12:00:00.
Program was meant to check date if it's expiring or expired, add it to proper list and display it after loops end.
public static void expiration_date(String filepath){
try {
DataInputStream read = new DataInputStream(new FileInputStream(filepath));
DateTimeFormatter format_day = DateTimeFormatter.ofPattern("uuuu/MM/dd");
DateTimeFormatter format_hour = DateTimeFormatter.ofPattern("HH:mm:ss");
LocalDate now_day = LocalDate.now();
LocalDateTime now_hour = LocalDateTime.now();
ArrayList<String> dates = new ArrayList<>();
ArrayList<String> expire_in_week = new ArrayList<>();
ArrayList<String> expire_tomorrow = new ArrayList<>();
ArrayList<String> expire_today = new ArrayList<>();
ArrayList<String> expired = new ArrayList<>();
while(read.available()>0) {
String name = read.readUTF();
String surname = read.readUTF();
String date = read.readUTF();
String cardcode = read.readUTF();
String cardtype = read.readUTF();
int contract_num = read.readInt();
String cert_num = read.readUTF();
String phone_num = read.readUTF();
String email = read.readUTF();
String status = read.readUTF();
String comment = read.readUTF();
dates.add(date);
for (String s:dates){
String[] data = s.split("/");
String days =data[0];
LocalDate date_days = LocalDate.parse(days.replace("-", "/"), format_day);
String hours =data[1];
LocalTime date_hours = LocalTime.parse(hours.replace("-", ":"),format_hour);
long daysbetween = ChronoUnit.DAYS.between(now_day,date_days);
long hoursbetween = ChronoUnit.HOURS.between(now_hour,date_hours);
if (daysbetween==7){
expire_in_week.add(cert_num);
}else if (daysbetween==1){
expire_tomorrow.add(cert_num);
}else if (daysbetween==0 && hoursbetween>0){
expire_today.add(cert_num);
}else if (daysbetween<0 || (daysbetween==0 && hoursbetween<0)){
expired.add(cert_num);
}else{}
}
}
System.out.println("Certificates that expires:");
System.out.println("Next week");
for (String w:expire_in_week){
System.out.print(w+"|");
}
System.out.println("Tomorrow");
for (String tm:expire_tomorrow){
System.out.print(tm+"|");
}
System.out.println("Today");
for (String td:expire_today){
System.out.print(td+"|");
}
System.out.println("Today");
for (String ex:expired){
System.out.print(ex+"|");
}
}catch(FileNotFoundException ex){ex.printStackTrace();}
catch(IOException ex){ex.printStackTrace();}
}
When i start it i got error message returned:
Exception in thread "main" java.time.DateTimeException: Unable to obtain LocalDateTime from TemporalAccessor: 12:00 of type java.time.LocalTime
at java.base/java.time.LocalDateTime.from(LocalDateTime.java:463)
at java.base/java.time.LocalDateTime.until(LocalDateTime.java:1677)
at java.base/java.time.temporal.ChronoUnit.between(ChronoUnit.java:272)
at com.company.program.expiration_date(program.java:189)
at com.company.program.main(program.java:364)
Caused by: java.time.DateTimeException: Unable to obtain LocalDate from TemporalAccessor: 12:00 of type java.time.LocalTime
at java.base/java.time.LocalDate.from(LocalDate.java:398)
at java.base/java.time.LocalDateTime.from(LocalDateTime.java:458)
... 4 more

The issue is because date_hours is of type LocalDateTime and date_hours is of type LocalTime. Try using the same type for both.
LocalTime now_hour = LocalTime.now();
Side note to parse the values of LocalDate and LocalTime you can try this
String data = "2022-01-23/12-00-00";
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd/HH-mm-ss");
LocalDate dateDays = LocalDate.parse(data, dateTimeFormatter);
LocalTime dateHours = LocalTime.parse(data, dateTimeFormatter);

See working example of your code here: https://github.com/RobbingDaHood/answers/blob/master/so70824574/src/Main.java
You LocalTime date_hours needs a timezone before it can be compared with LocalDateTime now_hour. So either add one to date_hours as I did in the code or remove the one from now_hour.
In my code the date_hours would get the system timezone, as the code is now. Be aware that maybe your file is not using that timezone.
Output of the example code is:
Certificates that expires:
Next week
Tomorrow
Today
Today
Cert1|
You can read more here
https://www.baeldung.com/java-8-date-time-intro
That will give you a good intro to the different date types in Java.

Java - How to get the correct date format with LocalDate

I've been having trouble correctly formatting the date as dd-MM-YYYY.
When I arrange the String dateString in the order of year-month-day, or year-day-month, it allows the date to be formatted.
It seems to only work when the yearParsed String as at the begginning of dateString.
Attempting to use DateTimeFormatter.ofPattern("dd-MM-YYYY") didn't seem to affect the date so it looks like I was not using it correctly.
Could you please let me know what I am doing wrong?
The user inputs a day, month and year one at a time, and I am looking to output the date as: 01-12-2000. The if/else are there to add a '0' in front, if the date or month input is a single digit.
Any help would be greatly appreciated.
Thank you!
String yearParsed = String.valueOf(year);
String monthParsed;
String dayParsed;
if (dayString.length() == 1) {
dayParsed = "0" + String.valueOf(day);
}
else {
dayParsed = String.valueOf(day);
}
if (monthString.length() == 1) {
monthParsed = "0" + String.valueOf(month);
}
else {
monthParsed = String.valueOf(month);
}
String dateString = yearParsed + "-" + monthParsed + "-" + dayParsed;
//String dateString = dayParsed + "-" + monthParsed + "-" + yearParsed;
System.out.println("dateString " + dateString);
LocalDate formattedDate = null;
DateTimeFormatter dateTimeFormatter;
dateTimeFormatter = DateTimeFormatter.ISO_LOCAL_DATE;
//dateTimeFormatter = DateTimeFormatter.ofPattern("dd-MM-YYYY");
formattedDate = formattedDate.parse(String.format(dateString, dateTimeFormatter));
System.out.println("Formatted Date = " + formattedDate);

Regarding your variable LocalDate formattedDate, you're misunderstanding the concept of formatted date.
A formatted date is a String, because you can control it's format.
When the object is a LocalDate instance, it contains value to determine a position in the time, when you just print it it has its default formatting, it you want one specific formatting you need a String representation of your date
String year = "2021", dayString = "1", monthString = "3";
LocalDate date = LocalDate.of(
Integer.parseInt(year),
Integer.parseInt(monthString),
Integer.parseInt(dayString)
);
System.out.println(date); // 2021-03-01
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd-MM-yyyy");
String formattedDate = date.format(dtf);
System.out.println("Formatted Date = " + formattedDate); // Formatted Date = 01-03-2021

You have used Y (week-based-year) instead of y (year-of-era). Learn the difference from the documentation and from answers to this question.
Simply create a LocalDate with the year, month and day and format it to a String using a DateTimeFormatter.
Demo:
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
int day = 12, month = 6, year = 2021;
LocalDate date = LocalDate.of(year, month, day);
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd-MM-uuuu", Locale.ENGLISH);
String formatted = dtf.format(date);
System.out.println(formatted);
}
}
Output:
2021-06-12
ONLINE DEMO
Here, you can use y instead of u but I prefer u to y.
Learn more about the modern Date-Time API from Trail: Date Time.
Note
A LocalDate is supposed to represent date units (year, month, day), and not a specific format. The default format used by LocalDate#toString is based on ISO 8601 standard. For a specific format, you need to format it into a String as shown above. It is like representing double d = 5.0 as the 5.000 which is done by formatting d into a String of this format.
public class Main {
public static void main(String[] args) {
double d = 5.0;
NumberFormat formatter = new DecimalFormat("#0.000");
String formatted = formatter.format(d);
System.out.println(formatted);
}
}
Output:
5.000

How to limited String in Android

In my application I want to show some text (date) into TextView.
I get this Text from server and I want to show this Text in TextView.
I get this Text from server :
16 Dec 2017
But I want to show such as this :
2017
How can I remove 16 Dec ?

try this
public static String getYyyy(String date) {
String time = date;
try {
SimpleDateFormat format = new SimpleDateFormat("dd MMM yyyy");
Date date1 = format.parse(date);
if (date1 != null) {
time = new SimpleDateFormat("yyyy").format(date1);
}
} catch (ParseException e) {
e.printStackTrace();
}
return time;
}

try this use split()
There are two signature for split() method in java string.
public String split(String regex)
and,
public String split(String regex, int limit)
use split a string in Java is to use .split(" ") which splits a string according to the pattern provided, returning a String array.
sample code
String date="16 Dec 2017";
String [] dateParts = date.split(" ");
String day = dateParts[0];
String month = dateParts[1];
String year = dateParts[2];

You can just separate the string with help of " " i.e. blank space, try to split the string with " " just like this:-
String date = "16 Dec 2017";
String[] date = date.split(" ");
//for only 2017 you can use date[2]

Be aware there are several ways more elegant and correct to do this, normally you use a Date object and just change how it looks like...
but to your wish, my answer:
I wouldnt split because is a waste to create an array for only getting one element of it...
you can use the substring method
String xdate = "16 Dec 2017";
System.out.println(xdate.substring(xdate.length() - 4, xdate.length()));

In java 8 you can do like this :
Date date = new Date(); //Create a Date object with date provided from TextBox
LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
int year = localDate.getYear();
int month = localDate.getMonthValue();
int day = localDate.getDayOfMonth();
Since you only want the year int year = localDate.getYear(); will give you year.

if you want substring of date in which only Year i.e. last 4 number then try below code
String date="16 Dec 2017";
int a = date.length();
String d = date.substring(a-4,a);

You can try this as well rather then split if you have date & time or more date data
String requested_date = "16 Dec 2017";
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd MMM yyyy");
Date dateObj = simpleDateFormat.parse(requested_date,new ParsePosition(0));
dateObj.getYear();

Using calendars or Joda-Time in java

I have a document that starts on date X and end on date Y and and goes up by one day. My task is to go through this document and find out how many days are missing from the document.
Example:
19990904 56.00
19990905 57.00
19990907 60.00
Need to print out that 19900906 is missing.
I have done some research and read about java calendar, Date, and Joda-Time, yet was unable to understand what any of them are. Can some one please explain what these functions I just mentioned do, and then make a suggestion on how to use one to accomplish my goal?
I already have this code:
String name = getFileName();
BufferedReader reader = new BufferedReader(new FileReader(name));
String line;
while ((line = reader.readLine()) != null)
{ //while
String delims = "[ ]+";
String [] holder = line.split(delims);
// System.out.println("*");
int date = Integer.parseInt(holder[0]);
//System.out.println(holder[0]);
double price = Double.parseDouble(holder[1]);

With JodaTime. (If you are only concerned with date, you should NOT use datetimes, or mess with hours,minutes, dst issues.)
final DateTimeFormatter dtf = DateTimeFormat.forPattern("yyyyMMdd");
LocalDate date=null;
while( (line = getNextLine())!=null) {
String dateAsString = line.split(delims)[0];
LocalDate founddate = dtf.parseLocalDate(dateAsString);
if(date==null) { date= founddate; continue;} // first
if(founddate.before(date)) throw new RuntimeException("date not sorted?");
if(founddate.equals(date)) continue; // dup dates are ok?
date = date.plusDays(1);
while(date.before(foundate)){
System.out.println("Date not found: " +date);
date = date.plusDays(1);
}
}
If you only need to count missing days:
LocalDate date=null;
int cont=0;
while( (line = getNextLine())!=null) {
String dateAsString = line.split(delims)[0];
LocalDate founddate = dtf.parseLocalDate(dateAsString);
if(date==null) { date= founddate; continue;} // first
if(founddate.before(date)) throw new RuntimeException("date not sorted?");
if(founddate.equals(date)) continue; // dup dates are ok?
cont += Days.daysBetween(date, founddate)-1;
date = founddate;
}

LocalDate x = new LocalDate(dateX);
LocalDate y = new LocalDate(dateY);
int i = Days.daysBetween(x, y).getDays();
missingdays = originalSizeofList - i;
This is joda-time, its much easier than vanilla java.

Java regex to extract date format out into month and year

Hi I have the following date string format:
June-2008
July-2008
March-2010
May I enquire what is the java regex to extract out whatever the month and year value into separate string each. The delimeter here is the "-" sign
Any values from the start to the end of the "-" sign is the month, anything after the "-" sign is the year value.
The following is what I would like to achieve
String m = March
String y = 2010
Thank all for your help!

Don't use a regex. Use String#split():
String[] parts = "June-2008".split("-", 2); // or .split("-")
String m = parts[0]; // "June"
String y = parts[1]; // "2008"
Even better, use SimpleDateFormat, and you'll have a proper Date to work with:
DateFormat df = new SimpleDateFormat("M-y");
Date myDate = df.parse("June-2008");

I want to extend the answer given by Matt Ball. If you want to split that string and willing to use other than String#split() you can use StringUtils of Apache Commons Lang. It has various String utility methods.
An example:
String strDate = "June-2008";
String[] parts = StringUtils.split(strDate, '-');
String month = parts[0]; // "June"
String year = parts[1]; // 2008
Also if you want to get a java.util.Date object then Joda Time may helps you. I personally prefer this api rather java.util.Date as it is far more rich, easy-to-use, less error-pron.
Now we can manipulate that String as:
String strDate = "June-2008";
DateTimeFormatter formatter = DateTimeFormat.forPattern("MMMM-yyyy");
DateTime dateTime = formatter.parseDateTime(strDate); // parse it
Date javaDate = dateTime.toDate(); // a java.util.Date object
int year = dateTime.getYear(); // 2008
String month = dateTime.month().getAsText(); // June
Hope this will help you. Thanks.