import javax.swing.*;
import java.awt.*;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
import java.awt.event.*;
public class ComboDemo extends JFrame
               implements ItemListener{
private Container container;
private JLabel lbDep,lbHeader,lbTel;
private JTextField tfHeader,tfTel;
private GridBagLayout Layout;
private GridBagConstraints constraints;
//系別信息字符串數組             
String[] strDep={"英語","數學","化學","物理","經濟"};
//系主任信息字符串數組 
String[] strHeader={"王巖","李煜","孫和平","吳江","張建"};
//聯系電話字符串數組   
String[] strTel={"13037272406","13937252408","13847825482",
         "13145678912","13536352409"};
private JComboBox cmbDep;
public ComboDemo() {
    super("組合框示例");
    setSize(260,200);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }
  //以設定的網格包布局向面板中添加組件
 private void addComponent(JPanel panel,GridBagLayout Layout,
                 GridBagConstraints gbc,Component com,int row,int column,
                      int numRows,int numColumns,int Weightx,int Weighty){
   gbc.gridx=row;
   gbc.gridy=column;
   gbc.gridwidth=numRows;
   gbc.gridheight=numColumns;
   gbc.weightx=Weightx;
   gbc.weighty=Weighty;
   Layout.setConstraints(com,gbc);
   panel.add(com);
 }
public void setLayout(){
   container=getContentPane();
   Layout=new GridBagLayout();
   container.setLayout(Layout);
   constraints=new GridBagConstraints();
   constraints.anchor=GridBagConstraints.CENTER;
   constraints.fill=GridBagConstraints.HORIZONTAL;
   //向框架內容面板添加組件
   lbDep=new JLabel("系別",JLabel.CENTER);
   addComponent((JPanel)container,Layout,constraints,lbDep,0,0,1,1,20,0);
   cmbDep=new JComboBox();
   cmbDep.addItemListener(this);
   addComponent((JPanel)container,Layout,constraints,cmbDep,1,0,1,1,80,100);
   lbHeader=new JLabel("系主任",JLabel.CENTER);
   addComponent((JPanel)container,Layout,constraints,lbHeader,0,1,1,1,20,0);
   tfHeader=new JTextField();
   addComponent((JPanel)container,Layout,constraints,tfHeader,1,1,1,1,80,100);
   lbTel=new JLabel("電話",JLabel.CENTER);
   addComponent((JPanel)container,Layout,constraints,lbTel,0,2,1,1,20,0);
   tfTel=new JTextField();
   addComponent((JPanel)container,Layout,constraints,tfTel,1,2,1,1,80,100);
 }
   private void addItem(){//向組合框添加項目信息
     for(int i=0;i<strDep.length;i++){
          cmbDep.addItem(strDep[i]);
     }
 }
  public static void main(String[] args) {
    ComboDemo frame = new ComboDemo();
    frame.setLayout();
    frame.addItem();
    frame.show();
  }
  public void itemStateChanged(ItemEvent e) {
    if(e.getSource() instanceof JComboBox){
      //獲取組合框的當前選項索引 
      int index=cmbDep.getSelectedIndex();
      //根據當前組合框的索引值，設置相應的文本框信息。
      tfHeader.setText(strHeader[index]);
      tfTel.setText(strTel[index]);
    }
  }
}