欧布奥特曼变身器安卓:java.lang.NullPointerException哪里不对啊

错误提示为:
java.lang.NullPointerException
at org.apache.jsp.add$jsp._jspService(add$jsp.java:66)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:201)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:381)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:473)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
-------------------------------------------------------------
jsp页面代码：
<%
ArrayList units=new ArrayList();
units=ZbiaoBean.getInstance().getUnit();

for(int i=0;i<=units.size();i++){
ArrayList unit=(ArrayList)units.get(i);
if(unit!=null)
{
%>
<input type="checkbox" name="checkbox" value="<%=(String)unit.get(0)%>" />
<%out.print((String)unit.get(1));out.print("<br>");
}
}%>
-----------------------------------------------------------
Zbiaobean.java代码为：
public static ArrayList getUnit()//throws IOException, ServletException
{
ArrayList t = new ArrayList();
Connection connection = null;
Statement statement = null;
try
{
ArrayList s;
connection = ConnectionMgr.getConnection();
statement = connection.createStatement();
//ResultSet res = statement.executeQuery("select * from unitzz");
for(ResultSet resultset = statement.executeQuery("select * from unitzz"); resultset.next();t.add(s))
{
s= new ArrayList();
s.add(resultset.getString("uid"));
s.add(resultset.getString("uzz"));

}

}
catch(java.sql.SQLException e)
{
e.printStackTrace();
if(connection!=null)try{
connection.close();
}
catch(Exception e2){}

}
return t;
}