Compute total from scanning string from left to right instead of right to left

I am basically trying to figure out a technique in which I can scan a string from left to right and it will give me the integer of it. Starting from right to left is quiet easy as shown in the code below. I am just struggling on finding a way to add each integer to make it the correct value it is supposed to be.

Output: Would you like to enter an expression? y enter an expression 2567 value = 7652

I am trying to get the output to be in the correct order.

e = String input // string needing to be converted to double  p = 0 // position  // If a substring of e whose rightmost character is at position p      // represents a number (possibly with a decimal point, possibly negative),      // return the numerical value of the substring as a double value and      // re-position p just to the left of the substring.        private double formNum() {            double total = 0.0;          int count = 0;          int flag = 0;          double mult = 1;          char c, d;          do {              c = e.charAt(p); // examine the current character in the string (from right to left)              if (c == '.') {                  flag = 1; // set a flag to remember that the character is a decimal point              } else {                  // if the current character is a digit, convert to its                  // int value and include it in the value corresponding to the string.                  if ((c >= '0') && (c <= '9')) {                                            total = total + mult * (c - '0');                      mult = mult * 10.0;                      if (flag == 0) {                          count++; // count the number of digits to the right of a possible decimal point                      }                  } else {                      if (c == '(' && e.charAt(p + 1) == '-') {                          total = -total; // an underscore character represents a negative value                      }                  }              }              p++; // Prepare to move to the next character to the left.                      // This is a private non-static method because it changes the member variable p              d = '?';              if (p <= e.length() - 1) {                  d = e.charAt(p); // the next character to the left              }          } while ((p <= e.length() - 1) && (((d <= '9') && (d >= '0')) || (d == '_') || (d == '.')));// check for a valid                                                                                                      // character          if (flag == 1) {              total = total / Math.pow(10, count * 1.0); // compute the value taking into account                                                          // the number of decimal places          }          return total;      }  

https://stackoverflow.com/questions/66057000/compute-total-from-scanning-string-from-left-to-right-instead-of-right-to-left February 05, 2021 at 11:05AM