leetcode String to Integer (atoi)(Java)

public class Solution {
public int myAtoi(String str) {
if (str == null || str.length() < 1 )
return 0;
str = str.trim();
int len = str.length();
long result = 0;
boolean negative = false;

int i = 0;
if (str.charAt(0) == '-')
{
negative = true;
++i;
}
else if (str.charAt(0) == '+')
{
++i;
}

while ((i < len) && (str.charAt(i) >= '0') && (str.charAt(i) <= '9'))
{
result = result * 10 + (str.charAt(i) - '0');
if (result > Integer.MAX_VALUE)
return (negative)?(Integer.MIN_VALUE):(Integer.MAX_VALUE);
++i;
}

if ((i == 1 && result == 0) || i == 0)
return 0;

if (negative == true)
result = -result;

return (int)result;
}
}