程序编译通过，但运行错误，错误提示后附程序：

Exception in thread "main" java.lang.IllegalArgumentException:illegal anchor value程序如下：
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
import javax.swing.border.Border;
import java.util.Vector;
public class Register_GUI{
  public Register_GUI(){
  RegisterFrame rf = new RegisterFrame();
  rf.setVisible(true);
  }
  public static void main(String[] args){
  new Register_GUI();
  }
}
class RegisterFrame extends JFrame{
private Toolkit tool;
public RegisterFrame(){
setTitle("用户名");
tool=Toolkit.getDefaultToolkit();
Dimension ds=tool.getScreenSize();
int w=ds.width;
int h=ds.height;
setBounds((w-300)/2,(h-300)/2,300,300);
setResizable(false);
RegisterPanel rp=new RegisterPanel(this);
add(rp);
}
}
class RegisterPanel extends JPanel implements ActionListener{
private JLabel titlelabel,namelabel,pwdlabel1,pwdlabel2,sexlabel,agelabel,classlabel;
private JTextField namefield,agefield;
private JPasswordField pwdfield1,pwdfield2;
private JButton commitbtn,resetbtn,cancelbtn;
private JRadioButton rbtn1,rbtn2;
private JComboBox combo;
private Vector<String>v;
private GridBagLayout gbl;
private GridBagConstraints gbc;
private JPanel panel;
private Box box;
private JFrame iframe;
public RegisterPanel(JFrame frame){
iframe=frame;
titlelabel=new JLabel("用户注册");
titlelabel.setFont(new Font("隶书",Font.BOLD,24));
namelabel=new JLabel("用户名: ");
pwdlabel1=new JLabel("密码: ");
pwdlabel2=new JLabel("确认密码: ");
sexlabel=new JLabel("性别: ");
agelabel=new JLabel("年龄:");
classlabel=new JLabel("所属班级:");
namefield=new JTextField(16);
pwdfield1=new JPasswordField(16);
pwdfield1.setEchoChar('*');
pwdfield2=new JPasswordField(16);
pwdfield2.setEchoChar('*');
agefield=new JTextField(16);
rbtn1=new JRadioButton("男");
rbtn2=new JRadioButton("女");
rbtn1.setSelected(true);
ButtonGroup bg=new ButtonGroup();
bg.add(rbtn1);
bg.add(rbtn2);
v=new Vector<String>();
v.add("软件英语053");
v.add("软件英语052");
v.add("软件英语051");
v.add("计算机应用051");
v.add("计算机应用052");
combo=new JComboBox(v);
commitbtn=new JButton("注册");
commitbtn.addActionListener(this);
resetbtn=new JButton("重置");
resetbtn.addActionListener(this);
cancelbtn=new JButton("取消");
cancelbtn.addActionListener(this);
panel=new JPanel();
panel.add(rbtn1);
panel.add(rbtn2);
Border border=BorderFactory.createTitledBorder("");
panel.setBorder(border);
box=Box.createHorizontalBox();
box.add(commitbtn);
box.add(Box.createHorizontalStrut(30));
box.add(resetbtn);
box.add(Box.createHorizontalStrut(30));
box.add(cancelbtn);
gbl=new GridBagLayout();
setLayout(gbl);
gbc=new GridBagConstraints();
addCompnent(titlelabel,0,0,4,1);
add(Box.createVerticalStrut(20));
gbc.anchor=GridBagConstraints.CENTER;
gbc.anchor=GridBagConstraints.HORIZONTAL;
gbc.weightx=0;
gbc.weighty=100;
addCompnent(namelabel,0,1,1,1);
addCompnent(namefield,1,1,4,1);
addCompnent(pwdlabel1,0,2,1,1);
addCompnent(pwdfield1,1,2,4,1);
addCompnent(pwdlabel2,0,3,1,1);
addCompnent(pwdfield2,1,3,4,1);
addCompnent(sexlabel,0,4,1,1);
addCompnent(panel,1,4,1,1);
gbc.anchor=GridBagConstraints.EAST;
gbc.fill=GridBagConstraints.NONE;
addCompnent(agelabel,2,4,1,1);
gbc.fill=GridBagConstraints.HORIZONTAL;
addCompnent(agefield,3,4,2,1);
addCompnent(classlabel,0,5,1,1);
addCompnent(combo,1,5,4,1);
gbc.anchor=GridBagConstraints.CENTER;
gbc.fill=GridBagConstraints.NONE;
addCompnent(box,0,6,4,1);
}
public void addCompnent(Component c,int x,int y,int w,int h){
gbc.gridx=x;
gbc.gridy=y;
gbc.gridwidth=w;
gbc.gridheight=h;
add(c,gbc);
}
public void actionPerformed(ActionEvent e){
if(e.getSource()==commitbtn){
  Register rinfo=new Register();
  rinfo.name=namefield.getText().trim();
  rinfo.password=new String(pwdfield1.getPassword());
  rinfo.sex=rbtn1.isSelected()?"男":"女";
  rinfo.age=agefield.getText().trim();
  rinfo.nclass=combo.getSelectedItem().toString();
  if(rinfo.name.length()==0){
  JOptionPane.showMessageDialog(null,"\t用户名不能为空");
  return;
  }
  if(rinfo.password.length()==0){
  JOptionPane.showMessageDialog(null,"\t密码不能为空");
  return;
  }
  if(!rinfo.password.equals(new String(pwdfield2.getPassword()))){
  JOptionPane.showMessageDialog(null,"密码两次输入不一致，请重新输入");
  return;
  }
  if(rinfo.age.length()==0){
  JOptionPane.showMessageDialog(null,"\t年龄不能为空");
  return;
  }
 int age=Integer.parseInt(rinfo.age);
  if(age<=0||age>100){
  JOptionPane.showMessageDialog(null,"\t年龄输入不合法");
  return;
  }
JOptionPane.showMessageDialog(null,"\t注册成功!");
}
  if(e.getSource()==resetbtn){
  namefield.setText("");
  pwdfield1.setText("");
  pwdfield2.setText("");
  rbtn1.isSelected();
  agefield.setText("");
  combo.setSelectedIndex(0);
  }
  if(e.getSource()==cancelbtn){
  iframe.dispose();
  }
}
}
class Register{
String name;
String password;
String sex;
String age;
String nclass;
}