i have a form with two fields. one is string and other int. than if user hit submit button than i am checking to see if there are errors. 1st error is if string is empty. 2nd error is if int field is empty. this is where i need help. i dont know how to check if int field is empty or not.

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>

     <form method="post" action="index.jsp">
		what's your name?<br/>
		<input type="text" name="usernameField"/><br/>
		what's your aga?<br/>
		<input type="text" name="ageField" /><br/>
		<input type="submit" name="submit" />
		if (request.getParameter("submit") != null) {
			String username = request.getParameter("usernameField");
			int number1 = Integer.parseInt(request.getParameter("ageField"));
			//check errors
				out.print("Error enter name");
			else if(number1 == 0)  //help here
				out.print("Error enter age");
				out.print("answer" + number1);

already tried these things but didnt worked:
int number1 = Integer.parseInt(request.getParameter("ageField"));

  if(request.getParameter("ageField") == null)
   if(number = null)