If the String has number inside then square the number and return as a String. How do i replace old number with the squared number Java

Question

So it should work like that

squareDigits("a22b") on "a44b"

squareDigits("a9b2") on "a81b4"

What I have got so far :

public class Code {
    public static void main(String[] args) {
        String ok = "a2b9";
        System.out.println(squareDigits(ok)); // "a81b4"
    }

  public static String squareDigits(String s) {
        char[] pena = s.toCharArray();
        int aboba;
        for (char c : pena) {
            if (Character.isDigit(c)) {
                String s1 = Character.toString(c);
                int b = Integer.parseInt(s1);
                aboba = b * b;
                System.out.println(aboba);
            }
        }
        return "";
        }
    }

Im only beginner and this would very help me out

why would that be the result? As far as I know: 22*22 is not 44 — Stultuske, Feb 11 '21 at 10:27
I would suggest having a look at the available methods in the `String` class, there are a number that might help, depending on the approach you want to take perhaps one of the `replace` methods? — Gavin, Feb 11 '21 at 10:27
Does your problem only consider single letter digits or multiple digits too? Could you please provide more sample test cases so that we could understand problem better? — Rohan Kumar, Feb 11 '21 at 10:28
@Joe I'm well aware of that, but 22 is a number as well, so according to how he explained it, it's not supposed to be looked at as 2 and 2, but as 22 — Stultuske, Feb 11 '21 at 10:29
Yes it should work only for single digits like "a55b" == "a2525b — Denis Suhachev, Feb 11 '21 at 10:36

score 0 · Answer 1 · answered Feb 11 '21 at 10:34

You can take a StringBuffer and iterate over char array and check if char is digit then square it and put into string buffer and if not char put it as it is in string buffer.

     public static void main(String[] args) {
        System.out.println(squareDigits("a22b"));
        System.out.println(squareDigits("a9b2"));
    }

    public static String squareDigits(String s) {
        char[] pena = s.toCharArray();
        StringBuffer sb = new StringBuffer();
        for (char c : pena) {
            if (Character.isDigit(c)) {
                String s1 = Character.toString(c);
                int b = Integer.parseInt(s1);
                sb.append(b * b);
            } else {
                sb.append(c);
            }
        }
        return sb.toString();
    }

score 0 · Answer 2 · answered Feb 11 '21 at 10:46

You can easily do it using StringBuilder like this:

public static void main(String[] args) {
    System.out.println(squareDigits("a22b")); // "a44b"
    System.out.println(squareDigits("a2b9")); // "a4b81"
    System.out.println(squareDigits("a55b")); // "a2525b"
}

public static String squareDigits(String s) {
    StringBuilder result = new StringBuilder();
    s.chars().forEach(c -> result.append(addDigitSquaredIfDigit(c)));

    return result.toString();
}

private static String addDigitSquaredIfDigit(int charAsDigit) {
    char c = (char) charAsDigit;
    return Character.isDigit(c) ? getSquaredDigitString(c) : String.valueOf(c);
}

private static String getSquaredDigitString(char c) {
    int digit = Integer.parseInt(Character.toString(c));

    return Integer.toString(digit * digit);
}

score 0 · Accepted Answer · answered Feb 11 '21 at 10:50

try as well.

public static void main(String[] args) {
    String ok = "a2b9";
    System.out.println(squareDigits(ok)); // "a81b4"
}

public static String squareDigits(String s) {
    StringBuilder sb = new StringBuilder();
    String[] chars = s.split("");
    for (String str : chars){
        if (isNumber(str)){
            int num = Integer.valueOf(str);
            Double square = Math.pow(num, 2);
            sb.append(square.intValue());
        } else {
            sb.append(str);
        }
    }
    return sb.toString();
}

private static boolean isNumber(String str) {
    try {
        Integer.valueOf(str);
        return true;
    } catch (Exception e) {
        return false;
    }
}

score 0 · Answer 4 · answered Feb 11 '21 at 10:59

A purely functional way (maybe not the most optimal one):

public static String squareDigits(String s) {
      char[] pena = s.toCharArray();
      return IntStream.range(0, pena.length).mapToObj(i -> pena[i]).map(it -> {
        String c = it.toString();
        try {
          int intVal = Integer.parseInt(c);
          return "" + (intVal * intVal);
        } catch (Exception e) {
          return c;
        }
      }).reduce("", String::concat);
}

If the String has number inside then square the number and return as a String. How do i replace old number with the squared number Java

4 Answers4