综合-把字符串转换成整数

public class Solution {
    /*
    解题思路：
    边界条件：数据上下 溢出；空字符串；有无正负号*/
    public int StrToInt(String str) {
        if (str.equals("") || str.length() == 0)
            return 0;
        char[] temp = str.toCharArray();
        int symbol = 0;//+
        if (temp[0] == '-')
            symbol = 1;//-
        int sum = 0;
        for (int i = symbol; i < temp.length; i++)
        {
            if (temp[i] == '+')
                continue;
            if (temp[i] < 48 || temp[i] > 57)//ASCII表48~57:0~9
                return 0;
            sum = sum * 10 + temp[i] - 48;
        }
        return symbol == 0 ? sum : sum * -1;
    }
}