Question First:

I don't know what's the definition of not using extra space. I can handle it without using any Math class function and Class objects but I think it would be crazy if you don't store any primitives like int.

My code with some extra int stored. (Not so succinct, sorry for that)

```
public class Solution {
public boolean isPalindrome(int x) {
if(x < 0) {
return false;
}
int r = 0; //r for the reverse code.
int i = 1;
int copy = x;
while(x != 0 && i < 10) { //be sure not to overflow.
r = r * 10 + x % 10;
x /= 10;
i++;
}
if(i != 10) {
if(r == copy) {
return true;
}
else {
return false;
}
}
else {
if(x == x % 10) {
r = r * 10 + x % 10;
if(r == copy) {
return true;
}
else {
return false;
}
}
else {
return false;
}
}
}
```

}