public class MathUtil {
public static void main(String[] args) {
int num = 1123;
int numDecimal = getDecimalValue(num);
System.out.println(num + " --> " + numDecimal);
}
private static int getDecimalValue(int num) {
int numDecimal = 0;
String numStr = String.valueOf(num);
for(int i = numStr.length() - 1, count = 0; i >= 0; i--){
numDecimal += Integer.parseInt(String.valueOf(numStr.charAt(i))) * Math.pow(7, count++);
}
return numDecimal;
}
}
----------------
1123 --> 409