In Java Swing, you can create a JComboBox cell editor for a JTable by implementing the TableCellEditor interface and using a JComboBox as the editor component. Here's an example:

import java.awt.Component;
import java.util.ArrayList;
import java.util.List;
import javax.swing.AbstractCellEditor;
import javax.swing.JComboBox;
import javax.swing.JTable;
import javax.swing.table.TableCellEditor;

public class ComboBoxEditor extends AbstractCellEditor implements TableCellEditor {
    private JComboBox<String> comboBox;
    private List<String> options;

    public ComboBoxEditor(List<String> options) {
        this.options = options;
        comboBox = new JComboBox<>(options.toArray(new String[0]));
    }

    @Override
    public Object getCellEditorValue() {
        return comboBox.getSelectedItem();
    }

    @Override
    public Component getTableCellEditorComponent(JTable table, Object value, boolean isSelected, int row, int column) {
        comboBox.setSelectedItem(value);
        return comboBox;
    }
}

In this example, we create a custom TableCellEditor implementation called ComboBoxEditor that uses a JComboBox as the editor component. The ComboBoxEditor constructor takes a List of options that will be used to populate the JComboBox.

The getCellEditorValue() method returns the currently selected item in the JComboBox. The getTableCellEditorComponent() method sets the selected item in the JComboBox to the current value of the cell being edited and returns the JComboBox component.

To use the ComboBoxEditor with a JTable, you would need to set the editor for the appropriate column. Here's an example of how to do this:

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingUtilities;
import javax.swing.table.DefaultTableModel;

public class TableExample {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            // Create a table with a default table model
            JTable table = new JTable(new DefaultTableModel(new Object[][]{{"Option 1"}, {"Option 2"}, {"Option 3"}}, new Object[]{"Options"}));

            // Set the editor for the second column to the ComboBoxEditor
            table.getColumnModel().getColumn(0).setCellEditor(new ComboBoxEditor(List.of("Option 1", "Option 2", "Option 3")));

            // Add the table to a scroll pane and display it in a frame
            JFrame frame = new JFrame();
            frame.add(new JScrollPane(table));
            frame.pack();
            frame.setVisible(true);
        });
    }
}

In this example, we create a JTable with a default table model and set the editor for the first column to the ComboBoxEditor we created earlier. When the user clicks on a cell in the first column, a JComboBox is displayed that allows them to select from the available options. When they select an option and press Enter, the selected option is displayed in the cell.