how to get a number from a file

Question

I have to get a number from a file, some files have letters and numbers convined. like (dsh8kuebw9) or have spaces like(8 8) how can I get those numbers? I have tried so many times. I have a method to find the occurences of a digit is in a number is the count8 method.

The parseInt converts the line of the file in a integer but because in some files there are letters I am having trouble with my method because it only accepts integers no Strings

File file_a = new File("C:\\name\\textFile8a.txt");
try 
{
    
    FileReader in = new FileReader(file_a);
    BufferedReader readFile = new BufferedReader(in);
    String n = readFile.readLine();
    int num = Integer.parseInt(n);
                
    
    System.out.println(count8(num, 8));
}
catch(IOException e)
{
    System.out.println("file could not be founded");
    System.err.println("OIException: " + e.getMessage());
}

Answer 1

You can remove all the numbers in your string before you parse it by replacing non-numberic characters with an empty string:

String n = readFile.readLine();
n = n.replaceAll("[^0-9]", "");
int num = Integer.parseInt(n);

Answer 2

basic and simple solution

public static ArrayList<Integer> extractNumber(String s) {

        ArrayList returnList = new ArrayList<Integer>();

        Pattern regex = Pattern.compile("\\d[\\d.]*");
        Matcher matcher = regex.matcher(s);
        while (matcher.find()) {
            returnList.add(matcher.group());
        }

        return returnList;
    }

    public static void main(String[] args) {

        File file_a = new File("C:\\name\\textFile8a.txt");
        try {

            FileReader in = new FileReader(file_a);
            BufferedReader readFile = new BufferedReader(in);
            String n = readFile.readLine();
            ArrayList<Integer> numberList = extractNumber(n);
            System.out.println(numberList);

        } catch (IOException e) {
            System.out.println("file could not be founded");
            System.err.println("OIException: " + e.getMessage());
        }
    }

Answer 3

Below is a method which will extract any signed or unsigned, Whole or Floating Point, numerical values from a supplied Input String of any length and return those values within a String[] Array. Read the method JavaDoc and the comments within the method:

/**
 * This method will extract all signed or unsigned Whole or floating point 
 * numbers from a supplied String. The numbers extracted are placed into a 
 * String[] array in the order of occurrence and returned.<br><br>
 * 
 * It doesn't matter if the numbers within the supplied String have leading 
 * or trailing non-numerical (alpha) characters attached to them.<br><br>
 * 
 * A Locale can also be optionally supplied so to use whatever decimal symbol 
 * that is desired otherwise, the decimal symbol for the system's current 
 * default locale is used. 
 * 
 * @param inputString (String) The supplied string to extract all the numbers 
 * from.<br>
 * 
 * @param desiredLocale (Optional - Locale varArgs) If a locale is desired for a 
 *               specific decimal symbol then that locale can be optionally 
 *               supplied here. Only one Locale argument is expected and used 
 *               if supplied.<br>
 * 
 * @return (String[] Array) A String[] array is returned with each element of 
 *               that array containing a number extracted from the supplied 
 *               Input String in the order of occurrence. If the supplied Input
 *               String was found to be null or empty then a 0 length String[] 
 *               Array is returned.
 */
public static String[] getNumbersFromString(String inputString, java.util.Locale... desiredLocale) {
    if (inputString == null || inputString.isEmpty()) {
        return new String[] {}; // Return a 0 length String Array.
    }
    // Get the decimal symbol the the current system's locale.
    char decimalSeparator = new java.text.DecimalFormatSymbols().getDecimalSeparator();
    
    /* Is there a supplied Locale? If so, set the decimal 
       separator to that for the supplied locale       */
    if (desiredLocale != null && desiredLocale.length > 0) {
        decimalSeparator = new java.text.DecimalFormatSymbols(desiredLocale[0]).getDecimalSeparator();
    } 
    /* The first replaceAll() removes all dashes (-) that are preceeded
       or followed by whitespaces. The second replaceAll() removes all
       periods from the input string except those that part of a floating 
       point number. The third replaceAll() removes everything else except 
       the actual numbers. */
   return  inputString.replaceAll("\\s*\\-\\s{1,}","")
                      .replaceAll("\\.(?![\\d](\\.[\\d])?)", "")
                      .replaceAll("[^-?\\d+" + decimalSeparator + "\\d+]", " ")
                      .trim().split("\\s+");
}

---

How you might use this method:

String filePath = "C:/name/textFile8a.txt";
String[] numbersArray = {};
// Get the decimal character used in the current System. 
char decimalSeparator = new java.text.DecimalFormatSymbols().getDecimalSeparator();
    
// 'Try With Resources' used to to auto-close the reader and free resources.
try (java.io.BufferedReader reader = new java.io.BufferedReader(new java.io.FileReader(filePath))) {
    String line;
    int lineCounter = 0; 
    while ((line = reader.readLine()) != null) {
        lineCounter++;
        System.out.println("File Line #" + lineCounter + " contains:");
        System.out.println("======================");
            
        line = line.trim();
        // Skip blank lines (if any).
        if (line.isEmpty()) {
            continue;
        }
        numbersArray = getNumbersFromString(line);  // ****
           
        /* Print the number(s) extracted from the file line 
           to the Console Window...         */
        for (String strgValue : numbersArray) {
            // Do what you want with the numerical values, for example:
            // Is this particular number a floating point value?
            if (strgValue.contains(Character.toString(decimalSeparator))) {
                // Yes it is...
                double dblValue = Double.parseDouble(strgValue);
                System.out.println("Extracted: -> " + dblValue);
            }
            else {
                //Nope..so it must be a Integer.
                int intValue = Integer.parseInt(strgValue);
                System.out.println("Extracted: -> " + intValue);
            }
                
            // Or just print them all out...
            // System.out.println(strgValue);
        }
        System.out.println();
    }
}
catch (FileNotFoundException ex) {
    System.out.println("File could not be found!");
}
catch (IOException ex) {
    System.err.println("OIException: -> " + ex.getMessage());
}

If the text file contained:

This is the #1 line.
This is version2.45 of the 2nd line
abcd4256.4efgha67klmn-56.2opqr-12stuvw666.78.
777 535 55 88 999
-56.765
dsh8kuebw9

and you run this file through the above code, the Console Window will display:

File Line #1 contains:
======================
Extracted: -> 1

File Line #2 contains:
======================
Extracted: -> 2.45
Extracted: -> 2

File Line #3 contains:
======================
Extracted: -> 4256.4
Extracted: -> 67
Extracted: -> -56.2
Extracted: -> -12
Extracted: -> 666.78

File Line #4 contains:
======================
Extracted: -> 777
Extracted: -> 535
Extracted: -> 55
Extracted: -> 88
Extracted: -> 999

File Line #5 contains:
======================
Extracted: -> -56.765

File Line #6 contains:
======================
Extracted: -> 8
Extracted: -> 9