• 全部代码

public class Solution {
    public int StrToInt(String str) {
              if (str.length() == 0) {
            return 0;
        }
            char[] arr = str.toCharArray();
            int flag = 0;
            if (arr[0] == '+') {
                flag = 1;
            }
            boolean tmp = false;
            if (arr[0] == '-') {
                tmp = true;
            }
            int sum = 0;

            if (flag == 1 || tmp == true) {
                for (int i = 1; i < arr.length; i++) {
                    if (arr[i] < '0' || arr[i] > '9') {
                        return 0;
                    }
                    sum += (arr[i] - '0') * Math.pow(10, arr.length - i - 1 );
                }
            } else {
                for (int i = 0; i < arr.length; i++) {
                    if (arr[i] < '0' || arr[i] > '9') {
                        return 0;
                    }
                    sum += (int)(arr[i] - '0') * Math.pow(10, arr.length - i - 1) ;
                }

            }
            return tmp ? sum * (-1) : sum;
    }
}