Why am I getting nullpointer error? - servlets

Question

To retrieve cookies from browsert, I wrote a simple function dispcookies(). When I compile, I got nullpointerException and then I just copied that code from dispcookies() and put in processRequest() that time I didn't get the error why it happens.
HttpServletRequest request;
HttpServletResponse response;
PrintWriter out=null;
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try {
out = response.getWriter();
String name=request.getParameter("name");
String phone=request.getParameter("phone");
Cookie cname=new Cookie("name",name);
Cookie cphone=new Cookie("phone",phone);
response.addCookie(cname);
response.addCookie(cphone);
out.println("here ok");
dispcookies ();
}
catch(Exception E)
{
out.println(E);
}
}
void dispcookies () throws IOException
{
Cookie[] cookies;
Cookie cookie;
cookies=request.getCookies();
if(cookies!=null)
{
for(int i=0;i<cookies.length;i++)
{
cookie=cookies[i];
out.println("cookie name"+cookie.getName());
out.println("cookie name"+cookie.getValue());
}
}
else
{
out.println("no foumd cooke ");
}
}

Answer 1

At void dispcookies () you are trying to access to a property of the attribute request. WARNING: This request IS NOT THE SAME that the input parameter of the processRequest method. dispcookies doesn't have visibility over these input parameter, only can see the attribute HttpServletRequest defined at the beginning of the class and this attribute has not been initialized so every access to it will cause a null pointer exception.
If you want to access to the processRequest' request input parameter you must change the dispcookies signature to accept this object as input parameter and use it.
By the way:
cookies=request.getCookies();
if(cookies!=null) {
for(int i=0;i ...
could cause a null pointer exception because Cookies[] can be not null but empty and you are accessing to its zero position without checking the emptyness of the array.