尝试运行时出现Java错误：“线程中的异常”主“

Question

所以我现在一直在做一个汽车锦标赛项目，但是当我想要运行该程序时，我似乎无法找到解决这个问题的方法。真的很沮丧。 ＆GT; _＆LT;

ERRORS: Exception in thread "main" java.lang.NullPointerException
    at javax.swing.ImageIcon.<init>(ImageIcon.java:217)
    at ReadData.StarterForm.initComponents(StarterForm.java:31)
    at ReadData.StarterForm.<init>(StarterForm.java:7)
    at ReadData.CarProgram.main(CarProgram.java:6)

这是我的代码：

/// MAIN ////

package ReadData;

public class CarProgram {

    public static void main(String[] args) {
       StarterForm startingPage = new StarterForm();
       startingPage.setVisible(true);
       /*Tournament tournament = new Tournament();
       tournament.round();*/
    }

}

//// StarterForm文件：/////

package ReadData;

public class StarterForm extends javax.swing.JFrame {


    public StarterForm() {
        initComponents();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        startButton = new javax.swing.JButton();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        jLabel6 = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(new java.awt.Color(0, 0, 0));

        jLabel1.setFont(new java.awt.Font("Times New Roman", 1, 48)); // NOI18N
        jLabel1.setText("Car Tournament ");

        jLabel2.setText("12 TEAMS ONE TOURNAMENT. BEST TIME WINS");

        startButton.setFont(new java.awt.Font("Times New Roman", 1, 36)); // NOI18N
        startButton.setIcon(new javax.swing.ImageIcon(getClass().getResource("/readdata/start-button.png"))); // NOI18N
        startButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                startButtonActionPerformed(evt);
            }
        });

        jLabel3.setIcon(new javax.swing.ImageIcon(getClass().getResource("/readdata/indy-500-checkered-flag-hhwQGx-clipart.gif"))); // NOI18N

        jLabel4.setIcon(new javax.swing.ImageIcon(getClass().getResource("/readdata/d26ac59dde3fdf0353f9fc35d2d5e871.jpg"))); // NOI18N

        jLabel5.setIcon(new javax.swing.ImageIcon(getClass().getResource("/readdata/d26ac59dde3fdf0353f9fc35d2d5e871.jpg"))); // NOI18N

        jLabel6.setFont(new java.awt.Font("Times New Roman", 0, 14)); // NOI18N
        jLabel6.setText("Done by : Anthony Reis, Chelsea Lutchman & Malcolm Lawrence");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addGap(182, 182, 182)
                                .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 250, javax.swing.GroupLayout.PREFERRED_SIZE))
                            .addGroup(layout.createSequentialGroup()
                                .addGap(132, 132, 132)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addComponent(jLabel6, javax.swing.GroupLayout.PREFERRED_SIZE, 378, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addComponent(jLabel1)))
                            .addGroup(layout.createSequentialGroup()
                                .addGap(209, 209, 209)
                                .addComponent(jLabel3)))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 78, Short.MAX_VALUE))
                    .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(startButton, javax.swing.GroupLayout.PREFERRED_SIZE, 109, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(217, 217, 217)))
                .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jLabel5, javax.swing.GroupLayout.DEFAULT_SIZE, 459, Short.MAX_VALUE)
            .addGroup(layout.createSequentialGroup()
                .addGap(5, 5, 5)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel1)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(jLabel6)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 200, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(startButton, javax.swing.GroupLayout.PREFERRED_SIZE, 0, Short.MAX_VALUE)
                        .addGap(9, 9, 9)))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void startButtonActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_startButtonActionPerformed
        GuiIntro intro = new GuiIntro(); //START GUIINTRO CLASS
        intro.setVisible(true); // MAKES IT VISIBLE 
        setVisible(false); //MAKES STARTERFORM HIDDEN
    }//GEN-LAST:event_startButtonActionPerformed

    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JButton startButton;
    // End of variables declaration//GEN-END:variables
}