Java下拉框JComboBox举例

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import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JComboBox;import javax.swing.JFrame;import javax.swing.JPanel;public class Demo10 extends JFrame implements ActionListener { String s[] = { "吉林", "辽宁", "黑龙江" }; String ss[][] = { { "吉林市", "长春市", "四平市" },    { "沈阳市", "大连市", "锦州市" },   { "佳木斯", "哈尔滨", "齐齐哈尔" } }; JComboBox jb1 = new JComboBox(s); JComboBox jb2 = new JComboBox(); JPanel panel = new JPanel(); public Demo10() {  panel.add(jb1);  panel.add(jb2);  jb1.addActionListener(this);  this.getContentPane().add(panel);  this.setBounds(100, 100, 300, 300);  this.setDefaultCloseOperation(3);  this.setVisible(true); } public static void main(String[] args) {  new Demo10(); } public void actionPerformed(ActionEvent e) {  JComboBox temp = (JComboBox) e.getSource();  String name = (String) temp.getSelectedItem();  if(jb2.getItemCount()!=0){   jb2.removeAllItems();   jb2.updateUI();   jb2.setSelectedItem("");  }  if(name.equals(s[0])){    for(int i=0;i<3;i++){    jb2.addItem(ss[0][i]);   }  }  else if(name.equals(s[1])){   for(int i=0;i<3;i++){    jb2.addItem(ss[1][i]);   }  }  else if(name.equals(s[2])){   for(int i=0;i<3;i++){    jb2.addItem(ss[2][i]);   }  } }}
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