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MainPanel.java
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MainPanel.java
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// -*- mode:java; encoding:utf-8 -*-
// vim:set fileencoding=utf-8:
// @homepage@
package example;
import java.awt.*;
import java.util.stream.Stream;
import javax.swing.*;
public final class MainPanel extends JPanel {
private MainPanel() {
super(new BorderLayout());
JComboBox<String> combo = new JComboBox<>(new String[] {"AAAAA", "BBBB", "CCC", "DD", "E"});
combo.setSelectedIndex(-1);
JButton b1 = new JButton("setSelectedIndex(0)");
JButton b2 = new JButton("setSelectedIndex(-1)");
JButton b3 = new JButton("setSelectedItem(null)");
b1.addActionListener(e -> combo.setSelectedIndex(0));
b2.addActionListener(e -> combo.setSelectedIndex(-1));
b3.addActionListener(e -> combo.setSelectedItem(null));
JPanel box = new JPanel(new GridLayout(0, 1, 10, 10));
Stream.of(b1, b2, b3, combo).forEach(box::add);
add(box, BorderLayout.NORTH);
setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
setPreferredSize(new Dimension(320, 240));
}
public static void main(String[] args) {
EventQueue.invokeLater(MainPanel::createAndShowGui);
}
private static void createAndShowGui() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (UnsupportedLookAndFeelException ignored) {
Toolkit.getDefaultToolkit().beep();
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException ex) {
ex.printStackTrace();
return;
}
JFrame frame = new JFrame("@title@");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.getContentPane().add(new MainPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}