3C-1. (ID_Tester) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 package practice; class ID{ /*싱글톤?*/ private static int counter = 0; private int id; public ID() { id = ++counter; } public int getId() { return id; } public static int getCounter() { return counter; } } public class ID_Tester_3C_1 { public static void main(String[] args) { ID a = new ID(); ID b = new ID();..