You must use arrays for this task:
import java.util.Scanner;
public class GhettoNumeralSystem07 {
public static void main(String[] args) {
Scanner console = new Scanner(System.in);
char[] input = console.nextLine().toCharArray();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < input.length; i++) {
if (input[i] == '0') {
sb.append("Gee");
}
else if (input[i] == '1') {
sb.append("Bro");
}
else if (input[i] == '2') {
sb.append("Zuz");
}
else if (input[i] == '3') {
sb.append("Ma");
}
else if (input[i] == '4') {
sb.append("Duh");
}
else if (input[i] == '5') {
sb.append("Yo");
}
else if (input[i] == '6') {
sb.append("Dis");
}
else if (input[i] == '7') {
sb.append("Hood");
}
else if (input[i] == '8') {
sb.append("Jam");
}
else if (input[i] == '9') {
sb.append("Mack");
}
}
System.out.println(sb.toString());
}
}