Swing Java Tutorial

Modes Description
AUTO_RESIZE_ALL_COLUMNSAdjusts all column widths proportionally.
AUTO_RESIZE_LAST_COLUMNAdjusts the rightmost column width only to give or take space as required by the column currently being altered.
AUTO_RESIZE_NEXT_COLUMNIf you're reducing the width of a neighboring column, the neighboring column will grow to fill the unused space. If you're increasing the width of a column, the neighboring column will shrink.
AUTO_RESIZE_OFFTurns off the user's ability to resize columns. The columns can still be resized programmatically.
AUTO_RESIZE_SUBSEQUENT_COLUMNSAdjusts the width by proportionally altering (default) columns displayed to the right of the column being changed.

import java.awt.BorderLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
public class ResizeTable {
  public static void main(String args[]) {
    final Object rowData[][] = { 
        { "1", "one",  "I" },
        { "2", "two",  "II" },
        { "3", "three", "III" }};
    final String columnNames[] = { "#", "English", "Roman" };
    final JTable table = new JTable(rowData, columnNames);
    JScrollPane scrollPane = new JScrollPane(table);
    String modes[] = { "Resize All Columns", "Resize Last Column", "Resize Next Column",
        "Resize Off", "Resize Subsequent Columns" };
    
    final int modeKey[] = { JTable.AUTO_RESIZE_ALL_COLUMNS, JTable.AUTO_RESIZE_LAST_COLUMN,
        JTable.AUTO_RESIZE_NEXT_COLUMN, JTable.AUTO_RESIZE_OFF,
        JTable.AUTO_RESIZE_SUBSEQUENT_COLUMNS };
    
    JComboBox resizeModeComboBox = new JComboBox(modes);
    ItemListener itemListener = new ItemListener() {
      public void itemStateChanged(ItemEvent e) {
        JComboBox source = (JComboBox) e.getSource();
        int index = source.getSelectedIndex();
        table.setAutoResizeMode(modeKey[index]);
      }
    };
    resizeModeComboBox.addItemListener(itemListener);
    JFrame frame = new JFrame("Resizing Table");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(resizeModeComboBox, BorderLayout.NORTH);
    frame.add(scrollPane, BorderLayout.CENTER);
    frame.setSize(300, 150);
    frame.setVisible(true);
  }
}