随机生成Z-A0-9的6位不重复的随机数（100000起）

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)];
            // 保证六位随机数之间没有重复的
            randomcode = randomcode + c;
        }
        return randomcode;
    }

    public static void main(String[] args) {
        LinkedHashSet