求助问题出在哪？

package com.ruanko.view;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.JTextComponent;

import com.ruanko.business.FileOperation;






public class JMainFrame extends JFrame{
    private JTextField numberTextField=null;
    private JTextField nameTextFiel=null;
    private JTextField phoneTextField=null;
    private JTextField emailTextField=null;
    private JTextField addressTextField=null;
    private JButton addButton;
    public  JMainFrame(){
        
        this.setSize(620,500);
        this.setTitle("通讯录");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JLabel label=new JLabel("欢迎进入通讯录系统");
        this.getContentPane().add(label);
        this.setLocation(300,200);
        this.setLayout(new FlowLayout());
        ImageIcon imageIcon=new ImageIcon("image//Contact.png");
        Image image=imageIcon.getImage();
        this.setIconImage(image);
        
        JPanel mainPanel=new JPanel();
        
        mainPanel.add(new JLabel("联系人路径"));
        JTextField pathTextField = new JTextField(43);
        String defaultPath="F:/contacts.txt";
        pathTextField.setText(defaultPath);
        mainPanel.add(pathTextField);
        
        mainPanel.add( new Label("编号："));
        JTextField numberTextField=new JTextField(12);
        mainPanel.add(numberTextField);
      
        mainPanel.add( new Label("姓名："));
        JTextField nameTextField=new JTextField(12);
        mainPanel.add(nameTextField);
        
        mainPanel.add( new Label("手机号："));
        JTextField phoneTextField=new JTextField(12);
        mainPanel.add(phoneTextField);
        
        mainPanel.add( new Label("email："));
        JTextField emailTextField=new JTextField(12);
        mainPanel.add(emailTextField);
        
        mainPanel.add( new Label("地址："));
        JTextField addressTextField=new JTextField(30);
        mainPanel.add(addressTextField);
        
        mainPanel.add(new JLabel("性别"));
        JRadioButton maleButton=null;
        JRadioButton femaleButton=null;
        maleButton=new JRadioButton("男");
        femaleButton=new JRadioButton("女");
        mainPanel.add(maleButton);
        mainPanel.add(femaleButton);
        ButtonGroup buttonGroup=new ButtonGroup();
        buttonGroup.add(maleButton);
        buttonGroup.add(femaleButton);
        maleButton.setSelected(true);
        
        mainPanel.add(new JLabel("关系："));
        JComboBox relationshipBox=null;
        String[] relationship={"同事","同学","亲戚","朋友"};
        relationshipBox=new JComboBox(relationship);
        mainPanel.add(relationshipBox);
        
        addButton=new JButton("新增联系人");
        addButton.addActionListener((ActionListener) new AddContactActionListener());
        mainPanel.add(addButton);
        
        this.setContentPane(mainPanel);
    }
     class AddContactActionListener implements ActionListener {
                public void actionPerformed(ActionEvent e) {
                    String number=numberTextField.getText();
                    JTextComponent nameTextField = null;
                    String name=nameTextField.getText();
                    String phone=phoneTextField.getText();
                    String email=emailTextField.getText();
                    String address=addressTextField.getText();
                    String contactInfor=number+"##"+name+"##"+phone+"##"+email+"##"+address;// TODO Auto-generated method stub
                    String filePath="F:/contacts.txt";
                    System.out.println(contactInfor);
                    FileOperation fileoperation=new FileOperation();
                    fileoperation.saveContact(contactInfor,filePath);
                }

      public static void main(String[] args){              （为什么这里显示错误，提示去掉static，但是去掉后又不能运行了）
        JMainFrame frame=new JMainFrame();
        frame.setVisible(true);
    }
    }
}