String to Integer

Implement function atoi to convert a string to an integer.

If no valid conversion could be performed, a zero value is returned.

If the correct value is out of the range of representable values, INT_MAX(2147483647) or INT_MIN (-2147483648) is returned.

Example

"10" => 10
"-1" => -1
"123123123123123" => 2147483647
"1.0" => 1

 public class Solution {
     public int myAtoi(String str) {
         if (str == null || str.length() == )
             return ;
         str = str.trim();
         if (str.length() ==  && (str.equals("+") || str.equals("-") || str.equals(".") || str.equals(""))) {
             return ;
         }
 
         boolean isPositive = true;
         long current = ;
 
         for (int i = ; i < str.length(); i++) {
             if (i ==  && str.charAt(i) == '+') {
                 continue;
             } else if (i ==  && str.charAt(i) == '-') {
                 isPositive = false;
             } else if (str.charAt(i) >= '' && str.charAt(i) <= '') {
                 current = current *  + str.charAt(i) - '';
                 if (isPositive && current > Integer.MAX_VALUE)
                     return Integer.MAX_VALUE;
                 if (!isPositive && -current < Integer.MIN_VALUE)
                     return Integer.MIN_VALUE;
             } else {
                 break;
             }
         }
 
         if (!isPositive) {
             current = -current;
         }
 
         return (int) current;
     }
 }