Question

This is in java.

How do I validate that a users input is 4 digits (for my code it is supposed to be a year for example "2003" ); this is what I have in a class that is separate from the main

public class Album {

    private String title;
    private String artist;
    private int releaseYear;

    public Album (String title, String artist) {

    this.title = title;
    this.artist = artist;
    this.releaseYear = 0;

}

public boolean setReleaseYear (String releaseYear) {

   if (releaseYear.matches("(\\d{3})" )){
        String cleanedReleaseYearString = releaseYear.replaceAll("(|\\-)"," ");
        this.releaseYear = Integer.parseInt(cleanedReleaseYearString);

        return true;
    } else {
         return false;
    }
}
public String getReleseYear() {

    String releaseYear = Integer.toString(this.releaseYear);
    String digit = releaseYear.substring(0,3);

    return "    " + digit;
}

***BACK IN MAIN***

public class Main {

    private static final String DATABASE_FILE_NAME = "database.txt";

    private static ArrayList<Album> albumCollection = new ArrayList<Album>();

    public static void main(String[] args) throws Exception {

boolean isReleaseYearSet = false;

while( !isReleaseYearSet ) {
    System.out.println("Enter year album was released in the formal 2019: ");
    String releaseYear = in.nextLine();
    System.out.println(" ");
    isReleaseYearSet = newAlbum.setReleaseYear(releaseYear);
}

}

I am taking the user input from the main class, and validating if it is a four digit numerical value (a year), It compiles but it continuously ask for input of year.

Answer 1

If you have any doubts, please give me comment...

The pattern that you are matching, that is incorrect. It matches only 3 digits. If 4 digits, it returns false. So that you have change for 4 digits.

Use this code in setReleaseYear method

if(releaseYear.matches("\\d{4}"))