I have a GregorianCalender in my entity class, how do i create an object which has specific date and display in specific format in toString()?

Question

public class Book {
    Calendar dateOfPublish;

    Book(Calendar dateOfPublish, ...){}

    public Calendar getDateOfPublish() {
        return dateOfPublish;
    }

    public void setDateOfPublish(int day, int month, int year) {
        this.dateOfPublish = dateOfPublish;
    }

    public String toString() {
                return Date Of Publish=" + dateOfPublish.YEAR + "/" + dateOfPublish.MONTH + "/" + 
                       dateOfPublish.DATE;
    }
}

I've tried to instantiate a book object using this this as argument in the Calendar data fielld.

new Book(new GregorianCalendar(2018,3,20));

But when i display the object with toString(), it displays

Results:    
Date Of Publish=1/2/5

I've searched through internet, seeing some people use SimpleDateFormat, but can it be done in an entity class? Or is there any better Date/Calendar class that i should use?

I recommend you don’t use `GregorianCalendar`. That class is poorly designed and long outdated. Instead use `LocalDate` from [java.time, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). — Ole V.V., Feb 27 '21 at 11:33

Arvind Kumar Avinash · Accepted Answer · 2021-02-27T11:31:59.810

You have declared your method with the completely reverse order of the parameters that you will find in the constructors of any date type available in Java.

public void setDateOfPublish(int day, int month, int year) {
    //...
}

The order of parameter in the method declaration should match with the order of arguments you pass to call it and therefore I suggest, you declare your method as follows to avoid accidents:

public void setDateOfPublish(int year, int month, int day) {
    //...
}

Also, the java.util date-time API and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern date-time API.

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.

Using the modern date-time API, you can do it as follows:

import java.time.LocalDate;

class Book {
    LocalDate dateOfPublish;

    // ...

    public void setDateOfPublish(LocalDate dateOfPublish) {
        this.dateOfPublish = dateOfPublish;
    }

    public void setDateOfPublish(int year, int month, int day) {
        this.dateOfPublish = LocalDate.of(year, month, day);
    }

    public String toString() {
        return "Date Of Publish=" + dateOfPublish;
    }
}

public class Main {
    public static void main(String[] args) {
        Book book1 = new Book();
        book1.setDateOfPublish(LocalDate.of(2018, 3, 20));
        System.out.println(book1);

        Book book2 = new Book();
        book2.setDateOfPublish(2020, 2, 10);
        System.out.println(book2);
    }
}

Output:

Date Of Publish=2018-03-20
Date Of Publish=2020-02-10

Learn more about the modern date-time API from Trail: Date Time.

score 1 · Answer 2 · answered Feb 27 '21 at 11:05

1

Use new classes:

LocalDate dateOfPublish = LocalDate.of(2018, 03, 2);
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd");
System.out.println(dtf.format(dateOfPublish));

For details referDateTimeFormatter

answered Feb 27 '21 at 11:05

the Hutt

16,980
2
14
44

score 0 · Answer 3 · answered Feb 27 '21 at 11:08

0

is these:

public String toString() {
        return "Date Of Publish = " + dateOfPublish.get(Calendar.YEAR) + " / " + dateOfPublish.get(Calendar.MONTH) + " / " +
                dateOfPublish.get(Calendar.DATE);
}

answered Feb 27 '21 at 11:08

quan he

3
3

It’s correct (except for the month). It’s not the recommended way to format a date into a string (better use a formatter). (And as I said elsewhere, it’s not recommended to use `GregorianCalendar` at all.) In any case thanks for your contribution. – Ole V.V. Feb 27 '21 at 11:56

I have a GregorianCalender in my entity class, how do i create an object which has specific date and display in specific format in toString()?

3 Answers3