在使用JTextField或JLabel的任何函数时，NULLPOINTEREXCEPTION的例外是存在的原因吗？我使用的是JDK 1.8.0_45

Question

package database;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class Oracle extends javax.swing.JFrame {
    public Oracle() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jTextField2 = new javax.swing.JTextField(10);
        jLabel2 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(null);
        getContentPane().add(jTextField2);
        jTextField2.setBounds(250, 50, 240, 20);

        jLabel2.setText("jLabel2");
        getContentPane().add(jLabel2);
        jLabel2.setBounds(150, 50, 80, 20);

        pack();
    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    static int x, y;
    static int number;
    static JTextField T1[];
    static JLabel L1[];
    public static void main(String args[]) {

        String str = JOptionPane.showInputDialog(null, "Enter Your host name/IP Addess"); //NOI18N


        try {

            Class.forName("oracle.jdbc.OracleDriver");
            Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@" +             str + ":1521:xe", "system", "9415");
            Statement s = conn.createStatement();
            String Table = JOptionPane.showInputDialog("Enter Table Name for which Records You Want to see"); //NOI18N
            ResultSet rs = s.executeQuery("select * from " +Table);
            ResultSetMetaData rsmd = rs.getMetaData();
            number = rsmd.getColumnCount();
            L1=new JLabel[number];
            T1=new JTextField[number];
            for (int i = 0; i < number; i++) { 
                L1[i] = new JLabel();
                T1[i] = new JTextField();
            }
            set();    

            rs.close();
            conn.close();
        } catch (ClassNotFoundException | SQLException ex) {
            JOptionPane.showMessageDialog(null, ex);
        }

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(() -> {
            new Oracle().setVisible(true);
        });

    }
    public static void set(){

        Oracle.jTextField2.setVisible(false);
        x=jTextField2.getX();
        y=jTextField2.getY();
        for(int i=0;i<number;i++){
            T1[i].setBounds(x, y*(i*25),jTextField2.getWidth(),jTextField2.getHeight() );
        }
    }

    // Variables declaration - do not modify                     
    private static javax.swing.JLabel jLabel2;
    private static javax.swing.JTextField jTextField2;
    // End of variables declaration                   
}