parsing for integers from user input in java?

Question

I want to get a rational number from the user in the form 188/4 for example and end up with int 188 and int 4. what is an efficient way to do this in java? is stringTokenizer the best way?? or is there something like scanf in c??

private int NUM;
private int DEN;
static Scanner s;
public Rational(){
    s = new Scanner(System.in).useDelimiter("/");
    System.out.println("Enter Rational number in the form of a/b:");
    NUM = s.nextInt();
    int d = s.nextInt();
    if(d == 0){
        throw new IllegalArgumentException();
    }
    else{
        DEN = d;
    }
}

when I run this my program freezes after I input a number

Your best option here is probably to read it in as a string, split the string based on "/" so that you end up with two strings. at that point, parse to see if both are integers, and you're all set — Neverwork2123
– Neverwork2123, Commented Feb 13, 2015 at 0:49

shirrine · Accepted Answer · 2015-02-13 01:29:26Z

1

Small tweaks...

private int NUM;
private int DEN;
static Scanner s;
public Rational(){
    System.out.println("Enter Rational number in the form of a/b:");
    s = new Scanner(System.in);
    String[] values = s.next().split("/");

    NUM = Integer.parseInt(values[0]);
    int d = Integer.parseInt(values[1]);
    if(d == 0){
        throw new IllegalArgumentException();
    } else{
        DEN = d;
    }
}

answered Feb 13, 2015 at 1:29

shirrine

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Comments

Nick Vasic · Accepted Answer · 2015-02-13 01:18:31Z

Try something like this (assuming each fraction can be input on a separate line):

        s = new Scanner(System.in).useDelimiter("\n");
        System.out.println("Enter Rational number in the form of a/b:");
        String in = s.nextLine();
        while (in.length() > 0) {
            if (in.contains("/")) {
                try {
                     NUM = Integer.parseInt(in.split("/")[0]);
                     DEN = Integer.parseInt(in.split("/")[1]);
                } catch (Exception e){
                    throw new IllegalArgumentException("Fraction must contain numeric values only");
                }
            } else {
                throw new IllegalArgumentException("Fraction must contain a '/' character");
            }
            System.out.println("NUM = " + NUM + " DEN = " + DEN);
            in = s.nextLine();
        }

dHoja · Accepted Answer · 2015-02-13 01:18:52Z

The only way i could think about is to treat is as a string, remove the unnecessary "/" and then turn it back into a int with Integer.parseInt();

  int NUM;
        int DEN;
        Scanner s;
            s = new Scanner(System.in).useDelimiter("/");
            System.out.println("Enter Rational number in the form of a/b:");
            String enteredString = s.nextLine();

            String firstString = "", secondString = "";
            StringBuilder sb = new StringBuilder(enteredString);

            boolean foundWeirdChar = false;
            boolean firstChar = true;
            char tempChar = '/';

            for(int i = 0; i < sb.length(); i++) {

                if(sb.charAt(i) == tempChar) {
                    foundWeirdChar = true;
                }

                if(!foundWeirdChar) {
                    firstString += sb.charAt(i);
                }else {
                    if(firstChar) { // Because the first char will be "/"
                        firstChar = false;
                    }else{
                     secondString += sb.charAt(i);
                    }
                }
            }
            int a = 0;
            int b = 0;
            try {
                a = Integer.parseInt(firstString);
                b = Integer.parseInt(secondString);

                System.out.println("First int: " + a + "\nSecond int: " + b);

            }catch(NumberFormatException ex) {
                ex.printStackTrace();
            }

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