Count number of digits in integer with Java

digits.java

  public static int stringBased(int number) {
        return String.valueOf(number).length();
    }

    public static int logarithmBased(int number) {
        return (int) Math.log10(number) + 1;
    }

    public static int repeatedMultiplication(int number) {
        int length = 0;
        long temp = 1;
        while (temp <= number) {
            length++;
            temp *= 10;
        }
        return length;
    }

    public static int powersOfTwo(int number) {
        int length = 1;
        if (number >= 100000000) {
            length += 8;
            number /= 100000000;
        }
        if (number >= 10000) {
            length += 4;
            number /= 10000;
        }
        if (number >= 100) {
            length += 2;
            number /= 100;
        }
        if (number >= 10) {
            length += 1;
        }
        return length;
    }

    public static int divideAndConquer(int number) {
        if (number < 100000) {
            if (number < 100) {
                if (number < 10) {
                    return 1;
                } else {
                    return 2;
                }
            } else {
                if (number < 1000) {
                    return 3;
                } else {
                    if (number < 10000) {
                        return 4;
                    } else {
                        return 5;
                    }
                }
            }
        } else {
            if (number < 10000000) {
                if (number < 1000000) {
                    return 6;
                } else {
                    return 7;
                }
            } else {
                if (number < 100000000) {
                    return 8;
                } else {
                    if (number < 1000000000) {
                        return 9;
                    } else {
                        return 10;
                    }
                }
            }
        }
    }