String to Integer (atoi)

Implement atoi to convert a string to an integer.

Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.

Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.

Update (2015-02-10):
The signature of the C++ function had been updated. If you still see your function signature accepts a const char * argument, please click the reload button to reset your code definition.
这题，想想清楚就好了。可以看看Integer.valueOf()
public class Solution {
public int atoi(String str) {
int  i = 0;
boolean negitive  = false;
String s = str.trim();
if(s == null ||"".equals(s)){
return 0;
}

if(s.charAt(0)=='-'){
negitive = true;
}
if(s.charAt(0) == '-'||s.charAt(0)=='+'){
s = s.substring(1);
}
i = translate(s, negitive);
if(i>0){
i = negitive?-i:i;
}

return i;
}
public int translate(String str,boolean b){
char[] arrays = str.toCharArray();
int end = 0;
for(int i =0;i<arrays.length;i++){

if(arrays[i]-48 <0||arrays[i]-48>9){
break;
}
if(!b){
if(end > 214748364){
return Integer.MAX_VALUE;
}else if(end == 214748364 && arrays[i]-48>7){
return Integer.MAX_VALUE;
}
}else{
if(end > 214748364){
return Integer.MIN_VALUE;
}else if(end == 214748364 && arrays[i]-48>8){
return Integer.MIN_VALUE;
}

}

end = end *10+(arrays[i]-48);

}

return end;

}
}