int a = Integer.parseInt(Integer.toString(9) + Integer.toString(10));
public static Integer concatenateInt(int a, int b) {
if(b < 0){
b *= -1;
}
int proxyB = b/10;
a *= 10;
for (; proxyB > 0; proxyB /= 10) {
a *= 10;
}
if(a < 0){
a -= b;
} else {
a += b;
}
return a;
}