Java图形化界面无法显示

界面会一闪而过无法显示出来，报错是:Cannot read field "parent" because "comp" is null
代码如下：
package com.file;

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;

import javax.swing.ButtonGroup;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;

public class Register {
JFrame jf;

JLabel jl_id, jl_password, jl_age, jl_sex, jl5;
JTextField jt_id, jt_password, jt_age, jt_sex;
JPanel jp1, jp2, jp3, jp4, jp5, jp6, jp_group, jp_img;
JButton jb1;
ButtonGroup group;
JRadioButton radioButton_student, radioButton_teacher, radioButton_manage;

public static void main(String[] args) {
new Register();

    }

public Register()  {
    jf = new JFrame("注册界面");
    jf.setSize(500, 700);
    jf.setLocation(1300,100);
    jf.setVisible(true);
    jf.setLayout(new GridLayout(7, 2));

    Icon img = new ImageIcon("tu1.gif");
    jp_img = new JPanel();
    jp_img.add(new JLabel(img));

    jl_id = new JLabel("用户名");
    jt_id = new JTextField(15);
    jp1 = new JPanel();
    jp1.add(jl_id);
    jp1.add(jt_id);
    jl_password = new JLabel("密码");
    jt_password = new JTextField(15);
    jp2 = new JPanel();
    jp2.add(jl_password);
    jp2.add(jt_password);

    jp_group = new JPanel();
    radioButton_student = new JRadioButton("学生");
    jp_group.add(radioButton_student);
    radioButton_teacher = new JRadioButton("老师");
    jp_group.add(radioButton_teacher);
    radioButton_manage = new JRadioButton("教务");
    jp_group.add(radioButton_manage);
    group = new ButtonGroup();
    group.add(radioButton_student);
    group.add(radioButton_teacher);
    group.add(radioButton_manage);

    jb1 = new JButton("完成");
    jp5 = new JPanel();
    jp5.add(jb1);
    jl5 = new JLabel("注册成功");
    jp6 = new JPanel();
    jf.add(jp_img);
    jf.add(jp1);
    jf.add(jp2);
    jf.add(jp_group);
    jf.add(jp5);
    jf.add(jp6);
    jb1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            //学生
            if (radioButton_student.isSelected()) {
                Student stu = new Student(jt_id.getText(), jt_password
                        .getText());
                if (IOStreamStudent.file.length() == 0) {
                    DB.arrStu.add(stu);
                    IOStreamStudent.writeToFile();
                    jp6.add(jl5);
                    jf.setVisible(true);
                    jt_id.setText("");
                    jt_password.setText("");
                } else {
                    DB.arrStu.clear();
                    DB.arrStu = IOStreamStudent.readFromFile();
                    Iterator<Student> it = DB.arrStu.iterator();
                    boolean flag = true;
                    while (it.hasNext()) {
                        Student newstu = it.next();
                        if (newstu.getId().equals(jt_id.getText())) {
                            flag = false;
                            JOptionPane.showMessageDialog(null,
                                    "此用户名已存在，请重新输入");
                        }
                    }
                    if (flag) {
                        if (!(jt_id.getText().isEmpty() || jt_password
                                .getText().isEmpty())) {
                            DB.arrStu.add(stu);
                            IOStreamStudent.writeToFile();
                            jp6.add(jl5);
                            jf.setVisible(true);
                            jt_id.setText("");
                            jt_password.setText("");
                        } else {
                            JOptionPane.showMessageDialog(null,
                                    "密码，用户名不能为空");
                        }
                    }
                }
            }
            //老师
            if (radioButton_teacher.isSelected()) {
                Teacher tea = new Teacher(jt_id.getText(), jt_password
                        .getText());
                if (IOStreamTeacher.file.length() == 0) {
                    DB.arrTea.add(tea);
                    IOStreamTeacher.writeToFile();
                    jp6.add(jl5);
                    jf.setVisible(true);
                    jt_id.setText("");
                    jt_password.setText("");
                } else {
                    DB.arrTea.clear();
                    DB.arrTea = IOStreamTeacher.readFromFile();
                    Iterator<Teacher> it = DB.arrTea.iterator();
                    boolean flag = true;
                    while (it.hasNext()) {
                        Teacher newtea = it.next();
                        if (newtea.getId().equals(jt_id.getText())) {
                            flag = false;
                            JOptionPane.showMessageDialog(null,
                                    "此用户名已存在，请重新输入");
                        }
                    }
                    if (flag) {
                        if (!(jt_id.getText().isEmpty() || jt_password
                                .getText().isEmpty())) {
                            DB.arrTea.add(tea);
                            IOStreamTeacher.writeToFile();
                            jp6.add(jl5);
                            jf.setVisible(true);
                            jt_id.setText("");
                            jt_password.setText("");
                        } else {
                            JOptionPane.showMessageDialog(null,
                                    "密码，用户名不能为空");
                        }

                    }
                }

            }
            //管理员
            if (radioButton_manage.isSelected()) {
                Manage man = new Manage(jt_id.getText(), jt_password
                        .getText());
                if (IOStreamManage.file.length() == 0) {
                    DB.arrMan.add(man);
                    IOStreamManage.writeToFile();
                    jp6.add(jl5);
                    jf.setVisible(true);
                    jt_id.setText("");
                    jt_password.setText("");
                } else {
                    DB.arrMan.clear();
                    DB.arrMan = IOStreamManage.readFromFile();
                    Iterator<Manage> it = DB.arrMan.iterator();
                    boolean flag = true;
                    while (it.hasNext()) {
                        Manage newman = it.next();
                        if (newman.getId().equals(jt_id.getText())) {
                            flag = false;
                            JOptionPane.showMessageDialog(null,
                                    "此用户名已存在，请重新输入");
                        }
                    }
                    if (flag) {
                        if (!(jt_id.getText().isEmpty() || jt_password
                                .getText().isEmpty())) {
                            DB.arrMan.add(man);
                            IOStreamManage.writeToFile();
                            jp6.add(jl5);
                            jf.setVisible(true);
                            jt_id.setText("");
                            jt_password.setText("");
                        } else {
                            JOptionPane.showMessageDialog(null,
                                    "密码，用户名不能为空");
                        }

                    }
                }

            }
        }

    });
}

}

现在运行没有报错了，控制台只有一大堆warnings

控制台错误信息贴上