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Thread: checking for digit while reading from a file

  1. #1
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    Default checking for digit while reading from a file

    guys, let's say I have a file that contains

    1
    33
    b s
    4
    10
    f
    a
    120
    5 6

    I want to count the numbers and letters, in my code I'm using the Character.isDigit(String.chartat(0)) to identify the numbers. But you can only use nextInt(); to read the input. this is very straight forward using next(), but how could I do it using nextInt();

    public static void main(String[] args) {
            mixedF();
        }
     
        public static void mixedF() {
            int numbers = 0; 
            int words = 0;
            String ch;      
            try {
                Scanner in = new Scanner(new File("myFile.txt"));
                while(in.hasNext()) {
                    ch = in.next();
                    if(Character.isDigit(ch.charAt(0)))
                        numbers++;
                    else
                        words++;              
                }
     
                System.out.println("numbrers: "+numbers);
                System.out.println("words: "+words);
            }
            catch (FileNotFoundException ex) { ex.getMessage(); }
     
        }


  2. #2
    Super Moderator jps's Avatar
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    Default Re: checking for digit while reading from a file

    I would suggest you read about the scanner class and become familiar with the methods available and their usage. Reading that page will answer your question and perhaps teach you even more useful things.

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    Default Re: checking for digit while reading from a file

    nextInt() will give you an error once it encounters a letter... how would you handle that?

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: checking for digit while reading from a file

    put the call to nextInt() inside of a try catch block to catch the error of trying to read a non-integer.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: checking for digit while reading from a file

    Quote Originally Posted by Norm View Post
    put the call to nextInt() inside of a try catch block to catch the error of trying to read a non-integer.
    this is my implementation, but I'm getting "imputMisMatchException"

    public static void mixedF() {
            int numbers = 0; 
            int words = 0;
            int num;      
            try {
                Scanner in = new Scanner(new File("myFile.txt"));
                while(in.hasNext()) {
                    try {
                        num = in.nextInt();
                        numbers++; 
                    }
                    catch (Error e) { words++; }              
     
                    }            
     
     
                System.out.println("numbrers: "+numbers);
                System.out.println("words: "+words);
            }

    Exception in thread "main" java.util.InputMismatchException

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: checking for digit while reading from a file

    java.util.InputMismatchException
    What does the API doc say for the method you are using?
    I'd expect that error if the data being read was not was expected. For example a letter instead of digits.

    What error condition did you want the catch block to handle? Use that in the catch block instead of Error.

    Read the API doc for the Error class to see when you should use that class.
    If you don't understand my answer, don't ignore it, ask a question.

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