How to convert from integer to month using array in Java

Question

Let's say if user needs to put some input in integer and the output will be in a month.

The first line of input is the number of members in a group. So for each of the following line there are 3 integers that represent a valid date which is the birthdate of each member in the format of dd mm yyyy. If a user insert number in for an example 1 01 2018 so output will become 1 January 2018.

This is my code.

import java.util.*;
import java.text.SimpleDateFormat;

public class LabExercise1b {

    public static void main(String[] args) {

        Scanner console = new Scanner(System.in);
        System.out.print(" "); //number of people
        int people = console.nextInt();
        int day, year;
        String[] month = new String[]{"January", "February", "March", "April", "May", "June", "July", "August",
                "September", "October", "November", "December"};

        for (int i = 1; i <= people; i++) {
            SimpleDateFormat newFormat = new SimpleDateFormat("MM");
            System.out.println(" ");
            day = console.nextInt();
            year = console.nextInt();
        }
        System.exit(0);
    }
}

Btw, i am still new on learning java language. Hopefully someone can teach me or share some knowledge. I am using eclipse IDE.

Answer 1

If your input is 11042018. And you want your output to be 11 April 2018, then Do something like this:

Scanner console = new Scanner(System.in);

String[] month = new String[]{"January", "February", "March", "April", "May", "June", "July", "August","September", "October", "November", "December"};

int input = console.nextInt();

String dateString = input.toString();
String day = dateString.subString(0, 1);
String monthNum = dateString.subString(1, 3);
int intMonthNum = Integer.toString(monthNum);
String year = dateString.subString(3, 7);

System.out.print(day + " ");

if(intMonthNum>0 && intMonthNum <13){
    System.out.print(month[intMonthNum-1]); 
}else{
    System.out.println("Enter correct month number"); 
}

System.out.print(" " + year);

Answer 2

Month as an enum is present in Java time API also which can be directly used:

import java.time.Month;
import java.util.Scanner;

public class Test {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        System.out.println(Month.of(num).name());

    }
}

If you are not allowed to use java-8 or above. You can use user-defined enum in that case with a function which returns Month given Month's value as integer. For example:

enum Month {
    JANUARY(1), 
    FEBRURAY(2),
    MARCH(3),
    APRIL(4),
    MAY(5),
    JUNE(6),
    JULY(7),
    AUGUST(8),
    SEPTEMBER(9),
    OCTOBER(10),
    NOVEMBER(11),
    DECEMBER(12);

    private int value;

    private Month(int value) {
        this.value = value;
    }

    public static Optional<Month> valueOf(int value) {
        return Arrays.stream(values())
                .filter(month -> month.value == value)
                .findFirst();
    }

}

public class Test {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        System.out.println(Month.valueOf(num).get());
    }
}

Answer 3

I understand from your code in the question that you are allowed to use a built-in date formatter. That’s also a good idea. But: (1) Do use the modern DateTimeFormatter (not the outdated and troublesome SimpleDateFormat). (2) Now you’re at it, use it for formatting the entire date (not just the month).

    DateTimeFormatter outputFormatter = DateTimeFormatter
            .ofLocalizedDate(FormatStyle.LONG)
            .withLocale(Locale.UK);

    Scanner console = new Scanner(System.in);
    int day = console.nextInt();
    int monthNumber = console.nextInt();
    int year = console.nextInt();
    LocalDate date = LocalDate.of(year, monthNumber, day);
    System.out.println(date.format(outputFormatter));

Example run:

1 01 2018
01 January 2018

Very often one would also use a DateTimeFormatter for parsing the user input in one go rather than parsing each number separately. Use your search engine to find examples.

Link: Oracle tutorial: Date Time explaining how to use java.time.