To convert string to number without using wrapper classes in Java

public class StringToNumber {

private static int convertToNumber(String numStr) {
int sum = 0;
char[] charAry = numStr.toCharArray();
int zeroAscii = (int) '0';
for (char ch : charAry) {
int tempAscii = (int) ch;
sum = (sum * 10) + (tempAscii - zeroAscii);
}
return sum;
}

public static void main(String[] args) {
System.out.println("\"1234\" == "+convertToNumber("1234"));
System.out.println("\"4321\" == "+convertToNumber("4321"));
System.out.println("\"101112\" == "+convertToNumber("101112"));

     // By using Wrapper class
     // System.out.println(Integer.parseInt("1111"));
    // System.out.println(Integer.valueOf("2222"));


}

}