JComboBoxModel三级联动

importjava.awt.event.ActionEvent; importjava.awt.event.ActionListener; importjavax.swing.DefaultComboBoxModel; importjavax.swing.JComboBox; importjavax.swing.JFrame; importjavax.swing.JPanel; publicclassComboBoxDemoextendsJFrame{ privateDefaultComboBoxModelmodel=newDefaultComboBo