I am studying about the converting int to string and string to int without using toString and parseInt method. I already made methods. However, I don't believe that my way of doing was the best. I would like to improve these function.For example, the first converts from String to int:public static int StringToint(String number)        int eachnumber = 0;    int intConvert = 48;    int reVal = 0;    int index;    int maxlen =number.length() - 1;        for(index = 0 ; index <= maxlen ; index++)    {        eachnumber = number.charAt(index);        eachnumber = eachnumber  - intConvert;        reVal = reVal + (eachnumber * (int) Math.pow(10, maxlen - index));    }    return reVal;}Second, for converting int to String:public static String IntToString(int number){    int StringConvet = 48;    int eachDigit = number;    int afterDivide = number;    String reVal = ;    while(afterDivide >0)    {        eachDigit = afterDivide % 10;        afterDivide = afterDivide / 10;        if(eachDigit == 0)        {            reVal += 0;        }        else if(eachDigit == 1)        {            reVal += 1;        }        else if(eachDigit == 2)        {            reVal += 2;        }        else if(eachDigit == 3)        {            reVal += 3;        }        else if(eachDigit == 4)        {            reVal += 4;        }        else if(eachDigit == 5)        {            reVal += 5;        }        else if(eachDigit == 6)        {            reVal += 6;        }        else if(eachDigit == 7)        {            reVal += 7;        }        else if(eachDigit == 8)        {            reVal += 8;        }        else if(eachDigit == 9)        {            reVal += 9;        }    }    String reVal2 = ;    for(int index =  reVal.length() -1 ; index >= 0 ; index--)    {        reVal2 += reVal.charAt(index);    }    return reVal2;}I am sure that the StringToint method is \$O(n)\$ and intToString method will be \$O(n^2)\$. However, I am really sure that there are ways to improve these two methods. Is there any way to improve these two functions?
Converting int value to String without using toString and parseInt method
java;interview questions;reinventing the wheel
To improve your intToString() method you should consider using a StringBuilder, and specifically the method StringBuilder.append(int).Iterate digits in your int, and for each digit you can append(eachDigit) to the StringBuilder element. This will also reduce the complexity of intToString() to \$O(n)\$ since you do not need to create a new String instance each iteration. To get a String object from the StringBuilder, use StringBuilder.toString(). Or, if you are not allowed, you can use StringBuilder.subString(0).You should also use a StringBuilder.append() (using the same idea) to reverse the resulting string (your second loop in your code).Since it is not homework (as per comments), I have no problems providing a code snap. It should look something like this:public static String intToString(int n) {     if (n == 0) return 0;    StringBuilder sb = new StringBuilder();    while (n > 0) {         int curr = n % 10;        n = n/10;        sb.append(curr);    }    String s = sb.substring(0);    sb = new StringBuilder();    for (int i = s.length() -1; i >= 0; i--) {         sb.append(s.charAt(i));    }    return sb.substring(0);}Notes:You can also use StringBuilder.reverse() instead of the second loop.In here, \$O(n)\$ means linear in the the number of digits in the input number (n is the number of digits in the input number - not the number itself!) If you are looking for the complexity in terms of the initial number (it is \$O(\log(n))\$) since you divide your element by 10 each iterations, you have a total of \$\log_{10}(\text{number})\$ iterations for each loop, which results in \$O(\log(\text{number}))\$.