关于servlet中getParameterValues()的报错问题

 login.html   

<form action="loginServlet1" method="post">	     user:<input type="text" name="user"/>	     passWord:<input type="password" name="password"/>	    	     <br><br>	     interesting:	     <input type="checkbox" name="interesting" value="book"/>book	     <input type="checkbox" name="interesting" value="song"/>song	     <input type="checkbox" name="interesting" value="sport"/>sport	     <input type="checkbox" name="interesting" value="eat"/>eat	     <input type="checkbox" name="interesting" value="sleep"/>sleep	     <input type="submit" value="Submit"/></form>loginServlet.java
public void service(ServletRequest request, ServletResponse response)			throws ServletException, IOException {         System.out.PRintln("请求来了。。。");         System.out.println(request);                  String user=request.getParameter("user");         String password=request.getParameter("password");         System.out.println("user:"+user+"  "+"password:"+password);                  String [] interestings=request.getParameterValues("interesting");         System.out.println("interesting:"+interestings[0]);         //如果不选的话会出错的         for(String interest:interestings)         {        	 System.out.println("interesting:"+interest);         } }如果多选框有选择，该程序运行正确。
结果：
如果多选框选择为空，程序在for循环处报错。
不是很清楚原因。