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Thread: Question about Scanner and String values

  1. #1
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    Default Question about Scanner and String values

    Hello! I'm a relative beginner and this is my first post, and it's somewhat of an obscure question, so hopefully I've got all my wording right!

    I'm working on a program, and in this program I have a Scanner object set up using an empty delimiter. The input is a date (e.g. 1997), so I have 4 String objects set to receive input so that I can use each numeral of the date seperately.

    Scanner scanner = new Scanner(System.in);
    String delim = new String();
    scanner.useDelimiter(delim);
     
    String a = new String();
    String b = new String();
    String c = new String();
    String d = new String();
     
    System.out.print("Please enter a year: ")
    a = scanner.next();
    b = scanner.next();
    c = scanner.next();
    d = scanner.next();

    Now, I had assumed that if, for example, I entered a 3-character string for my input, my fourth String, d, would remain "null" but that is not in fact the case. When concatenated with other strings it seems to be a newline character of some sort. When checked for length it has a length of 1. But when compared to System.getProperty("line.seperator") or "\n" it returns false, using both the .equals method of the String class and the boolean == operator. I'd really like to know what the value that is being assigned to this String is (or rather how to represent that value in Java) so that I can use it for the sake of comparison in my program.

    If anyone can help, that'd be great. Or, if you think I need to further clarify what I'm trying to ask, please let me know! Thanks!


  2. #2
    Super Moderator pbrockway2's Avatar
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    Default Re: Question about Scanner and String values

    May be the following will shed some light:

     
    import java.util.Scanner;
     
    public class Foo {
        public static void main(String[] args) {
            Scanner scanner = new Scanner(System.in);
            String delim = new String();
            scanner.useDelimiter(delim);
     
                // (A)
            String a = new String();
            String b = new String();
            String c = new String();
            String d = new String();
     
                // (B)
            System.out.print("Please enter a year: ");
            a = scanner.next();
            b = scanner.next();
            c = scanner.next();
            d = scanner.next();
     
                // (C)
            System.out.println("-->" + d + "<--");
            System.out.println("\n".equals(d));
            System.out.println((int)d.charAt(0));
            System.out.println((int)"\n".charAt(0));
     
                // (D)
            String e = scanner.next();
            System.out.println("\n".equals(e));
     
                // (E)
            String real = System.getProperty("line.separator");
            System.out.println("d+e is the real line separator: " + (d+e).equals(real));
            String bogus = System.getProperty("line.seperator");
            System.out.println("d+e is the bogus line separator: " + (d+e).equals(bogus));
        }
    }

    (I'm assuming a Windows OS)

    I was going to comment on all of that, but am too lazy! Ask if anything is unclear. Notice I didn't bother to initialise e with "new String()" as it seems a bit redundant to give a variable a value and then assign it another.

    I think I would read the whole line and use the string method toCharArray() for a task like this.

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