Binding list of object in spring mvc

public class Contact {

    private String firstname;
    private String lastname;
    private String email;
    private String phone;

    public Contact() {
    }

    public Contact(String firstname, String lastname, String email, String phone) {
        this.firstname = firstname;
        this.lastname = lastname;
        this.email = email;
        this.phone = phone;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }
}

public class ContactForm {

    private List<Contact> contacts;

    public List<Contact> getContacts() {
        return contacts;
    }

    public void setContacts(List<Contact> contacts) {
        this.contacts = contacts;
    }
}

This is my Controller class

@Controller
public class ContactController {

    private List<Contact> list = new ArrayList<Contact>();

    @RequestMapping(value = "/save", method = RequestMethod.POST)
    public ModelAndView save(@ModelAttribute("contactForm") ContactForm contactForm) {
        System.out.println(contactForm);
        System.out.println(contactForm.getContacts());
        List<Contact> contacts = contactForm.getContacts();

        if(null != contacts && contacts.size() > 0) {
            for (Contact contact : contacts) {
                System.out.printf(contact.getFirstname());
            }
        }

        return new ModelAndView("showContact", "contactForm", contactForm);
    }
}

And below is my jsp

<%@taglib uri="http://ift.tt/18bwTB1" prefix="spring"%>
<%@taglib uri="http://ift.tt/IED0jK" prefix="form"%>
<%@taglib uri="http://ift.tt/QfKAz6" prefix="c"%> 

<h2>Spring MVC Multiple Row Form Submit example</h2>
<form:form method="post" action="save.html" modelattribute="contactForm">
    <c:forEach items="${contactForm.contacts}" var="contact" varStatus="status">
       </c:forEach><table>
    <tbody><tr>
        <th>No.</th>
        <th>Name</th>
        <th>Lastname</th>
        <th>Email</th>
        <th>Phone</th>
    </tr>
    <tr>
            <td align="center">${status.count}</td>
            <td><input name="contact[${status.index}].firstname" value="${contact.firstname}"></td>
            <td><input name="contact[${status.index}].lastname" value="${contact.lastname}"></td>
            <td><input name="contact[${status.index}].email" value="${contact.email}"></td>
            <td><input name="contact[${status.index}].phone" value="${contact.phone}"></td>
        </tr>

</tbody></table>  

<br>
<input type="submit" value="Save">

</form:form>

I got this code from viralpatel's blog, but its not working for me... First of all instead of showing multiple row as shown in that blog it show just one row. Secondly, in that very row if I am entering values it throws an error. Below is the full stack trace

SEVERE: Servlet.service() for servlet [MVC-Dispatcher] in context with path [/SpringMVC] threw exception [Request processing failed; nested exception is org.springframework.beans.InvalidPropertyException: Invalid property 'contacts[]' of bean class [com.sharique.beans.ContactForm]: Invalid index in property path 'contacts[]'; nested exception is java.lang.NumberFormatException: For input string: ""] with root cause
java.lang.NumberFormatException: For input string: ""
    at java.lang.NumberFormatException.forInputString(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at java.lang.Integer.parseInt(Unknown Source)
    at org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:793)
    at org.springframework.beans.BeanWrapperImpl.getNestedBeanWrapper(BeanWrapperImpl.java:571)
    at org.springframework.beans.BeanWrapperImpl.getBeanWrapperForPropertyPath(BeanWrapperImpl.java:548)
    at org.springframework.beans.BeanWrapperImpl.setPropertyValue(BeanWrapperImpl.java:916)
    at org.springframework.beans.AbstractPropertyAccessor.setPropertyValues(AbstractPropertyAccessor.java:95)
    at org.springframework.validation.DataBinder.applyPropertyValues(DataBinder.java:749)
    at org.springframework.validation.DataBinder.doBind(DataBinder.java:645)
    at org.springframework.web.bind.WebDataBinder.doBind(WebDataBinder.java:189)
    at org.springframework.web.bind.ServletRequestDataBinder.bind(ServletRequestDataBinder.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.bindRequestParameters(ServletModelAttributeMethodProcessor.java:150)
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:110)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:129)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:777)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:706)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)