Java Classic Programming question 50-way 48

A company uses a public telephone to pass data, the data is a four-bit integer, is encrypted during delivery, encryption rules are as follows: Each digit is added 5, and then divided by the remainder of 10 instead of the number, and then the first and fourth exchange, the second and third exchange.

public class Example48 {
public static void Main (string[] args) {
f (2345);
}

public static void f (int num) {
Int[] C = new Int[4];
if (num > 999 && num < 10000) {
C[0] = num/1000;
C[1] = (num/100)% 10;
C[2] = (NUM/10)% 10;
C[3] = num% 10;
for (int j = 0; J < 4; J + +) {
C[J] + = 5;
C[J]%= 10;
}
for (int j = 0; J <= 1; j + +) {
int temp = C[j];
C[J] = C[3-j];
C[3-J] = temp;
}
System.out.print ("The number after encryption is:");
for (int j = 0; J < 4; J + +)
System.out.print (C[j]);
} else {
SYSTEM.OUT.PRINTLN ("The data transmitted is wrong, please retry!!!" ");
}
}
}

Java Classic Programming question 50-way 48