public class Demo5 {

	public static void main(String[] args) {

		 char[] arr={'s','b','g','h','a','c'};

		StringBuilder sb=new StringBuilder();

		Random  random=new Random();

		for(int i=0;i<4;i++){

			int index=random.nextInt(arr.length);

			sb.append(arr[index]);

		}

		System.out.println("验证码:"+sb);

	} 

}