java 生成随机的6位字符

 public static void main(String[] args) {
        String a = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        char[] rands = new char[6]; 
        for (int i = 0; i < rands.length; i++) 
        { 
            int rand = (int) (Math.random() * a.length()); 
            rands[i] = a.charAt(rand); 
        } 
        for(int i=0;i<rands.length;i++){
            System.out.println(rands[i]);
        }
    }