public class InvertCodeGenerator {

    public static String generateRandomStr(int len) {
        String randomcode = "";
        String model = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        char[] m = model.toCharArray();
        for (int j = 0; j < 6; j++) {
            char c = m[(int) (Math.random
 
() * 36)];
            // 保證六位隨機數之間沒有重複的
randomcode = randomcode + c;
        }
        return randomcode;
    }

    public static void main(String[] args) {
        LinkedHashSet<Object> set = new LinkedHashSet<>();
        do{
            set.add(generateRandomStr(6));
        }
        while 
 
(set.size()<100000);
        for (Object str : set) {
            System.out.println(str);
        }
    };

}