How to pre-select JComboBox item by index in Java?

The following is an example to pre-select JComboBox item by index in Java. Here, we have selected the 3^rd item by default i.e. whenever the Swing program will run, the third item would be visible instead of the 1^st.

Example

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class SwingDemo {
   public static void main(String[] args) {
      JPanel panel = new JPanel(new BorderLayout());
      String[] strArr = new String[] { "Laptop", "Mobile", "Desktop", "Tablet" };
      JComboBox<String> comboBox = new JComboBox<>(strArr);
      panel.add(comboBox, BorderLayout.NORTH);
      JTextArea text = new JTextArea(5, 5);
      panel.add(text, BorderLayout.CENTER);
      JButton btn = new JButton("Click");
      // selecting the index
      comboBox.setSelectedIndex(2);
      btn.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            text.setText((String) comboBox.getSelectedItem());
            comboBox.setSelectedIndex(0);
         }
      });
      panel.add(btn, BorderLayout.SOUTH);
      JFrame frame = new JFrame();
      frame.add(panel);
      frame.pack();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

The output is as follows. The 3rd item is by default selected i.e. index 2:

Output

Here, you can check all the items: