需求

无需多言

代码

public static String cheakcode(){
        String base="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        Random r = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 5; i++) {
            int index = r.nextInt(base.length());
            char c = base.charAt(index);
            sb.append(c);
        }
        return sb.toString();
    }