Java Classic Programming question 50-way eight

The value of S=A+AA+AAA+AAAA+AA...A, where a is a number. For example 2+22+222+2222+22222 (a total of 5 numbers are added at this time), several numbers are added by keyboard control.

public class Example08 {
public static void Main (string[] args) {
SUM (2, 5);
}

public static void sum (int a, int n) {
int b = A;
Long sum = 0;
for (int i = 0; i < n; i++) {
sum + = A;
A = A * ten + B;
}
System.out.println ("and for:" + sum);
}
}

Java Classic Programming question 50-way eight