null pointer exception

[Matthew Phillips]

When I run the following code, I get this for output:
test2=after certifications
dates=[Ljava.lang.String;@116ab8
test1=beginning
alumniID=532797326
before calling certs=certs
error=java.lang.NullPointerException
before calling skills=sk
test3=after dates

import java.io.* ;
import javax.servlet.* ;
import javax.servlet.http.* ;
import java.util.* ;
public class RegistrationAction extends ActionBase
{
    List sqlStatements ;
    public void process( HttpServletRequest req , HttpServletResponse res )
        throws Exception
    {
        sqlStatements = new ArrayList();
        if( validate( req ) )
        {
            writeUser( req );
            writeAlumni( req );
            req.setAttribute( "before calling skills" , "sk" );
//            writeSkills( req );
            req.setAttribute( "before calling certs" , "certs" );
            writeCertifications( req );
//            writeEmployer( req );
            req.setAttribute( "url" , "/error.jsp" );
            req.setAttribute( "invalidLogin" , "You have successfully registered.  Please log in." );
        }
        else
        {
            req.setAttribute( "error" , "Fields marked with * are required.  Press the back button and make sure this are filled in." );
            req.setAttribute( "url" , "/error.jsp" );
        }
    }
    
    
    private boolean validate( HttpServletRequest req ) throws Exception
    {
        boolean isValid = true ;
        String validate = req.getParameter( "login" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        Iterator prevUsedID = DBAccess.getInformation( "Select userID from users where userID =\'" + validate + "\'" ).listIterator();
        if( prevUsedID.hasNext() )
        {
            req.setAttribute( "prevUsed" , "The login " + validate + " has already been used.  Please select another login." );
            isValid = false ;
        }
        
        validate = req.getParameter( "firstName" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        validate = req.getParameter( "lastName" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        validate = req.getParameter( "homePhone" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        validate = req.getParameter( "city" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        validate = req.getParameter( "state" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        validate = req.getParameter( "zip" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        validate = req.getParameter( "program" );
        if( ( validate == null ) || ( validate.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        String password = req.getParameter( "password" );
        if( ( password == null ) || ( password.equals( "" ) ) )
        {
            isValid = false ;
        }
        
        String confirm = req.getParameter( "confirm" );
        if( ( confirm == null ) || ( confirm.equals( "" ) ) || !( confirm.equals( password ) ) )
        {
            isValid = false ;
        }
        
        return isValid ;
    }
    
    
    private void writeUser( HttpServletRequest req ) throws Exception
    {
        String userName = req.getParameter( "login" ).toLowerCase();
        String firstName = req.getParameter( "firstName" );
        String lastName = req.getParameter( "lastName" );
        String email = req.getParameter( "email" );
        String homePhone = req.getParameter( "homePhone" );
        String userType = "alumni" ;
        String password = req.getParameter( "password" );
        
        sqlStatements.add( "Insert into users(userID, firstName, lastName, email, homePhone, userType , password) values(\'" + userName + "\', \'" +
            firstName + "\', \'" + lastName + "\', \'" + email + "\', \'" + homePhone + "\', \'" + userType + "\', \'" + password + "\')" );
    }
    
    
    private void writeSkills( HttpServletRequest req ) throws Exception
    {
        String skills[] = req.getParameterValues( "skills" );
        String alumniID = (String)req.getAttribute( "alumniID" );
        for( int i = 0 ; i < skills.length ; i++ )
        {
            if( skills[i] != null )
            {
                 sqlStatements.add( "Insert into alumni_skill(alumniID, skillID) values(\'" + alumniID + "\', \'" + skills[i] + "\')" );
            }
        }
    }
    
    
    private void writeCertifications( HttpServletRequest req ) throws Exception
    {
        req.setAttribute( "test1" , "beginning" );
        String[] certifications = req.getParameterValues( "certifications" );
        req.setAttribute( "test2" , "after certifications" );
        req.setAttribute( "cts" , certifications );
        String[] certificationDates = req.getParameterValues( "certDate" );
        req.setAttribute( "test3" , "after dates" );
        req.setAttribute( "dates" , certificationDates );
        String alumniID = (String)req.getAttribute( "alumniID" );
        for( int i = 0 ; i < certifications.length ; i++ )
        {
            req.setAttribute( "cert" , certifications[i] );
            req.setAttribute( "certD" , certificationDates[i] );
            if( certifications[i] != null )
            {
                 sqlStatements.add( "Insert into alumni_certification(alumniID, certificationID, certificationdate)" + 
                     " values(\'" + alumniID + "\', \'" + certifications[i] + "\', " + certificationDates[i]  + "\')" );
            }
        }
    }
    
    
    private void writeAlumni( HttpServletRequest req ) throws Exception
    {
        String alumniID = KeyFieldGenerator.getKeyField( "alumniID" , "alumni" );
        req.setAttribute( "alumniID" , alumniID );
        String userID = req.getParameter( "login" );
        String street = req.getParameter( "stAddress" );
        String city = req.getParameter( "city" );
        String state = req.getParameter( "state" );
        String zip = req.getParameter( "zip" );
        String major = req.getParameter( "program" );
        String grade = req.getParameter( "gpa" );
        double gpa = -1.0 ;
        if( ( grade != null ) && !( grade.equals( "" ) ) )
        {
            try
            {
                gpa = Double.parseDouble( grade );
            }
            catch( NumberFormatException e )
            {
                
            }
        }
        
        sqlStatements.add( "Insert into alumni ( alumniID, userID, street, city, state, zip, gpa, major ) values (\'" +
            alumniID + "\', \'" + userID + "\', \'" + street + "\', \'" + city + "\', \'" + state + "\', \'" + zip + "\', \'" +
            gpa + "\', \'" + major + "\')" );
    }
    
    
    private void writeEmployer( HttpServletRequest req ) throws Exception
    {
        String employerName = req.getParameter( "employer" );
        if( ( employerName !=null ) && !( employerName.equals( "" ) ) )
        {
            String phone = req.getParameter( "wkPhone" );
            String street = req.getParameter( "employerAddress" );
            String city = req.getParameter( "employerCity" );
            String state = req.getParameter( "employerState" );
            String zip = req.getParameter( "employerZip" );
            String employerID = KeyFieldGenerator.getKeyField( "employerID" , "employer" );
            
            sqlStatements.add( "Insert into employer columns( employerid, employername, employerphone, employerStreet, employercity, employerstate, employerzip)" +
                " values (\'" + employerID + "\', \'" + employerName + "\', \'" + phone + "\', \'" + street + "\', \'" + city + "\', \'" +
                state + "\', \'" + zip + "\')" );
                
            String alumniID = (String)req.getAttribute( "alumniID" );
            String jobTitle = req.getParameter( "jobTitle" );
            String jobDuties = req.getParameter( "jobDuties" );
            String date = req.getParameter( "startDate" );
            
            sqlStatements.add( "Insert into alumni_employer columns (alumniID, employerID, jobTitle, dateStarted, jobDuties) values (\'" +
                alumniID + "\', \'" + employerID + "\', \'" + jobTitle + "\', \'" + date + "\', \'" + jobDuties + "\')" );
            
        }
    }

If I comment out any references to req that occur after calling writeSkills, the program works. It seems that somewhere req is being set to null. Is there anything that I am missing?

[Matthew Phillips]

I found the problem. I was not accounting for getParameterValues returning null.