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  1. #1
    Join Date
    Sep 2003

    Question help input/output numbers

    I'm new to Java and this forum. I'm teaching myself java with a book I bought but I'm stuck on this one.

    This program is supposed to read 3 numbers and add each digit of that number. Like if I type in 123 it should output 6 (because 1+2+3 = 6). Non negatives and more than 1000 are not allowed. The program should quit if I type 1000 or negatives.

    This is what I have so far, but for some reason, I have to type in the number twice to get a result. I think I messed up on the if else statement.

    There is a method called Area51.readLine() and Area51.readNonwhiteChar(). I made those to "log" what the user types in.

    Anybody please help me see what I am overlooking here.

    Thanks. El chupacabra
    /* code begins here */
    public class Area51
        public static void main(String[] args)
    	System.out.println("Enter 3 numbers on one line. Then press Enter.");
            char n1,n2,n3;
            int all3, number_not_allowed;
            String over4chars;
    	//reads the numbers the users just typed in
    	over4chars = Area51.readLine();
            //calculates the lenght of that line and stores it
            number_not_allowed = over4chars.length();
    	//will read every character of that line
          	n1 = Area51.readNonwhiteChar();
    	n2 = Area51.readNonwhiteChar();
            n3 = Area51.readNonwhiteChar();
            //it was always off by 144 points so I implemented this workaround
            //all 3 characters are added
            all3 = (n1+n2+n3)-144;   
            //if the length of the number entered is more than 4 the program will quit
            //otherwise, it will process the numbers just fine
            if ((number_not_allowed > 3) || (number_not_allowed < 0)) 
    		System.out.println("This number is not allowed here punk.");
            System.out.println("The sum of the digits in " + n1 + n2 + n3 + " is " + all3);
    [ArchAngel added 'code' tags - please use in future]

  2. #2
    Join Date
    Mar 2003
    You've haven't posted the code which does all of the I/O (which is probably where your error is)!

    I've re-written your program. You'll see I do a few things differently to you. I've listed them here because when you first start to program, it's good to get into good habits early - bad habits are much harder to get out of.

    1. I do the length check FIRST. What's the point in calculating something if it's going to be wrong?

    2. I use generally more expressive variable names e.g. 'digit1' rather than 'n1' (the variable 'number_not_allowed' doesn't actually contain the number not allowed - it contains the length of the input!).

    3. I don't have any "workarounds". I can't urge you strongly enough to never go down this route, all you will do is provide a temporarily fix which you will promptly forget about. This will then result in hack, upon hack, upon hack - making your code harder to understand, harder to maintain and more prone to bugs.

    4. Your range check wouldn't catch the error if only 2 digits were entered.

    5. I've tried to limit the scope of all the variables as much as possible - only declaring them when they're necessary.
    import java.io.*;
    public class Area51 {
    	public static void main(String[] args) throws IOException {
    		System.out.print("Enter 3 numbers and then press [enter]: ");
    		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    		String line = br.readLine();
    		if (line.length() != 3) {
    			System.out.println("Invalid length.");
    		else {
    			int digit1 = Character.getNumericValue(line.charAt(0));
    			int digit2 = Character.getNumericValue(line.charAt(1));
    			int digit3 = Character.getNumericValue(line.charAt(2));
    			int sum = digit1 + digit2 + digit3;
    			System.out.println("The sum of the " + digit1 + ", " + digit2 + " and " + digit3 + " is " + sum);

  3. #3
    Join Date
    Sep 2003

    Thumbs up thank you so much

    dude, you da man! Thank you so much.

    I really appreciate your tips and for being cool to newbies.

    el chupacabra

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