I'm trying to create a calendar class in which I initial a default date. When a user creates the class the default Constructor is assigning the value "01-01-2012". If the user enters a valid date as a string parameter the second constructor will assign the new date.If not I would like the class to give a friendly warning this is not a valid date and go ahead and keep the default assignment.( eg. If the user enter "02/31/2012". This would throw the warning and go ahead and create the instance while setting the default to "01-01-2021".) I also created a method to set the date so this can be changed later once they give a valid date. How should i the second constructor in order to do this? Or is there a better more efficient process in order to do this?
import java.time.*;
import java.time.format.DateTimeFormatter;
public class CalendarDate {
private String date;
private DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMMMM dd uuuu");
//constructor sets date to January 1, 2012
CalendarDate(){
date = "01-01-2012";
};
/**
* Initializes object's chosen date
*
* @param day - initializes day
* @param month - initialazes month
* @param year - initialazes year
*/
public CalendarDate(String date){
this.date = date;
} // 1 - parameter Constructor
/**
*
* Sets new date given to this object
*
* @param date sets new date to object
*/
public void setDate(String date){
this.date = date;
}
/**
*
* Returns objects set date.
*
* @return Returns set date.
*/
public String getDate(){
LocalDate getDate = LocalDate.parse(date);
String formattedDate = getDate.format(formatter);
return formattedDate;
}
/**
*
* Returns object's date
*
* @return Returns object's date
*/
public String getNextDate(){
LocalDate dateTime = LocalDate.parse(date);
LocalDate returnValue = dateTime.plusDays(1);
String newNextDate = formatter.format(returnValue);
return newNextDate;
}
/**
* Returns prior date from the object's given date.
*
* @return
*/
public String getPriorDate(){
return " ";
}
/**
* Returns the day of the week from the object's given date.
*
* @return
*/
public String getDayOfWeek(){
return " ";
}
}
public class Calendar extends CalendarDate{
public static void main(String[] args){
CalendarDate testDate = new CalendarDate("06-07-1992");
testDate.getDate();
}
}
This is what I have so far and I'm wanting to use LocalDate and DateTimeFormatter. Anything will help.
CodePudding user response：
The format specified in the DateTimeFormatter must match the input string e.g.
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
String strDate = "01-01-2012";
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd-MM-uuuu", Locale.ENGLISH);
LocalDate date = LocalDate.parse(strDate, dtf);
System.out.println(date);
// Output in a custom format
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMMM dd uuuu", Locale.ENGLISH);
String formatted = formatter.format(date);
System.out.println(formatted);
}
}
Output:
2012-01-01
January 01 2012
Learn more about the modern Date-Time API* from Trail: Date Time.
* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8 APIs available through desugaring and How to use ThreeTenABP in Android Project.
CodePudding user response：
I offer the following suggestions to your design. I think they will also fix your error as a side effect if you had one.
private String date;
Don’t keep your date as a string. Keep it as a LocalDate object. Just like you keep numbers in int variables and Booelan values in boolean variables, not in strings. So the declaration becomes:
private LocalDate date;
This obviously means we will have to change much of the code in your methods.
CalendarDate(){
date = "01-01-2012";
};
In the above constructor you may use one of the of factory methods of LocalDate. For exmaple:
date = LocalDate.of(2012, Month.JANUARY, 1);
You have got:
* @param day - initializes day
* @param month - initialazes month
* @param year - initialazes year
It seems your Javadoc parameters don’t agree with your constructor here, and you need to fix them.
public CalendarDate(String date){
this.date = date;
} // 1 - parameter Constructor
It can be convenient to have a constructor that takes a String argument. In your Javadoc comment remember to mention the expected format of the string. Since I have now changed date to be a LocalDate, you need to parse the string before assigning to date. I suggest that you let any DateTimeParseException propagate out of the method so the user knows if parsing goes wrong. Also in your Javadoc document that the method may throw:
* @throws DateTimeParseException
* if the string is not in the expected format or does not denote a valid date
Further:
public void setDate(String date){
Again a method that is probably convenient and that will now need to parse the string. And throw an exception if appropriate.
public String getDate(){
LocalDate getDate = LocalDate.parse(date);
String formattedDate = getDate.format(formatter);
return formattedDate;
}
You can now simplify the above method a bit since it no longer needs to parse the date, only to format it. The same holds true for at least one more method.