Java: having issues to parse object.toString to LocalDate using java.time

Question

I am working on a problem set, and trying to build a class that returns dates. For this question, I need to return the day of week e.g. "Monday", "Tuesday" for a given date. I searched on Stack Overflow, and decided to try using java.time:

package Chapter1.Section2;

import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.util.Locale;

public class exercise_1_2_12 {
    private int day;
    private int month;
    private int year;

    public exercise_1_2_12(int month, int day, int year){
        if (!isDateValid(month, day, year)){
            throw new IllegalArgumentException("Invalid Date!");
        }
        this.month = month;
        this.day = day;
        this.year = year;
    }

    public int day(){
        return day;
    }

    public int month(){
        return month;
    }

    public int year(){
        return year;
    }

    public String toString(){
        //return month() + "-" + day() + "-" + year();
        return  year + "/" + String.format("%02d", month) + "/" + 
        String.format("%02d", day);
    }

    public boolean isDateValid(int month, int day, int year) {
        int[] dayInEachMonthLeapYr = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        int[] dayInEachMonthNonLeapYr = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        boolean valid = true;


        if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) {
            if (year < 1 || month < 1 || month > 12 || day < 1 || day > dayInEachMonthLeapYr[month - 1]) {
                valid = false;
            }
        } else {
            if (year < 1 || month < 1 || month > 12 || day < 1 || day > dayInEachMonthNonLeapYr[month - 1]) {
                valid = false;
            }
        }
        return valid;
    }

    public String dayOfWeekName(){
        DateTimeFormatter format = DateTimeFormatter.ofPattern("mm/dd/yyyy");
        String input = this.toString();
        LocalDate date = LocalDate.parse(input, format);
        DayOfWeek dayOfWeek = date.getDayOfWeek();
        String result = dayOfWeek.getDisplayName(TextStyle.FULL, Locale.US);
        return result;
    }

    public static void main(String[] args){

        StdOut.print("Enter month: ");
        int month = StdIn.readInt();
        StdOut.print("Enter day: ");
        int day = StdIn.readInt();
        StdOut.print("Enter year: ");
        int year = StdIn.readInt();
        exercise_1_2_12 smartDate = new exercise_1_2_12(month,day,year);
        StdOut.println(smartDate);
        smartDate.dayOfWeekName();
    }
}

The problems might be in the instance method dayOfWeekName(), I tried to parse the object this. to String format, then store it in LocalDate date, then return the name of the weekday. I tested it, the error message is the following:

Enter month: 4
Enter day: 1
Enter year: 2018
2018/04/01
Exception in thread "main" java.time.format.DateTimeParseException: Text '2018/04/01' could not be parsed at index 2
at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1949)
at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
at java.time.LocalDate.parse(LocalDate.java:400)
at Chapter1.Section2.exercise_1_2_12.dayOfWeekName(exercise_1_2_12.java:64)
at Chapter1.Section2.exercise_1_2_12.main(exercise_1_2_12.java:85)

Process finished with exit code 1

I am not quite sure how to solve this issue.

By the way, you could replace your isDateValid method by simply trapping for DateTimeException while calling LocalDate.of: try{ LocalDate ld = LocalDate.of( y , m , d ) ; } catch ( DateTimeException e ) { … handle invalid input … } — Basil Bourque
– Basil Bourque, Commented Mar 31, 2018 at 23:38

acdcjunior · Accepted Answer · 2018-03-31 22:15:52Z

2

Have a look at your date pattern:

DateTimeFormatter format = DateTimeFormatter.ofPattern("mm/dd/yyyy");

The date:

'2018/04/01'

Naturally does not match it.

Either enter a date in that pattern, like:

'04/01/2018'

Or change the pattern:

DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy/MM/dd");

Important: As precisely pointed by @Ivar in comments, also note that the pattern for months is uppercase M. When you you use mm, it matches minutes instead.

edited Mar 31, 2018 at 22:15

answered Mar 31, 2018 at 22:11

acdcjunior

136k37 gold badges341 silver badges312 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

acdcjunior Over a year ago

@Ivar, you are absolutely right. Usually it takes me a run to spot those patterns. Good eye! Thank you!

RiffRaffCat Over a year ago

Thanks a lot! Should have used "yyyy/MM/dd" format instead. Indeed, mm denotes to minute instead of month!

Svichkarev Anatoly · Accepted Answer · 2018-03-31 22:16:12Z

-1

Use this formatter:

DateTimeFormatter.ofPattern("MM/dd/yyyy")

answered Mar 31, 2018 at 22:16

Svichkarev Anatoly

7496 silver badges14 bronze badges

Collectives™ on Stack Overflow

Java: having issues to parse object.toString to LocalDate using java.time

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related