getting NullPointerException, how can I fix it? [duplicate]

This question already has an answer here:

• What is a NullPointerException, and how do I fix it? 12 answers

Good day, Getting a null pointer exception in my preparedeStatement.executeUpdate(), not sure of what I'm doing wrong. Please any help will be appreciated:

public void addVisitor(){
        try {
            String insert = "INSERT INTO mydb.visitor"+"(visitor_id, suname,names,gender,visited_date,phone,email,address,suburb,area_code,city,country)"+"VALUES(?,?,?,?,?,?,?,?,?,?,?,?)";

            preparedStatement = connection.prepareStatement(insert);

            preparedStatement.setInt(1, details.getVisitorID());
            preparedStatement.setString(2, details.getSurname());
            preparedStatement.setString(3, details.getNames());
            preparedStatement.setString(4, details.getGender());
            preparedStatement.setString(5, details.getVisitDate());
            preparedStatement.setString(6, details.getPhone());
            preparedStatement.setString(7, details.getEmail());
            preparedStatement.setString(8, details.getAddress());
            preparedStatement.setString(9, details.getSuburb());
            preparedStatement.setInt(10, details.getArea());
            preparedStatement.setString(11, details.getCity());
            preparedStatement.setString(12, details.getCountry());

            preparedStatement.executeUpdate(insert);

        } catch(SQLException e){

            e.printStackTrace();
        }

    }

and my db as only one primary key which is the visitor_id.

Stack trace:

java.lang.NullPointerException
at labornechurch.DatabaseTransaction.addVisitor(DatabaseTransaction.java:91)
at labornechurch.AddVisitor.jButton1ActionPerformed(AddVisitor.java:477)
at labornechurch.AddVisitor.access$100(AddVisitor.java:20)
at labornechurch.AddVisitor$2.actionPerformed(AddVisitor.java:355)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)