Auto resizing the JTable column widths

You can try the next:

public void resizeColumnWidth(JTable table) {
    final TableColumnModel columnModel = table.getColumnModel();
    for (int column = 0; column < table.getColumnCount(); column++) {
        int width = 15; // Min width
        for (int row = 0; row < table.getRowCount(); row++) {
            TableCellRenderer renderer = table.getCellRenderer(row, column);
            Component comp = table.prepareRenderer(renderer, row, column);
            width = Math.max(comp.getPreferredSize().width +1 , width);
        }
        if(width > 300)
            width=300;
        columnModel.getColumn(column).setPreferredWidth(width);
    }
}

This needs to be executed before the resize method.
If you have:

table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

There is no option to automatically resize one column larger than the other.

Maybe you can to something like:

tca = new TableColumnAdjuster( table, 0 );
tca.adjustColumns();
TableColumnModel tcm = table.getColumnModel();  
TableColumn tc = tcm.getColumn(1);
tc.setWidth(tc.getWidth() + 25);

This would allow you to add extra space to column 1. This extra space would only be added the first time the table is displayed.

Another option is to use:

table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS);

This would allocate extra space proportionally to each column.

setAutoResizeMode() will tell your table how to resize you should give it a try will all different options available to see the differences, in My case I wanted to specifically resize two columns and let it decide how to adjust all the other ones.

jTable1.setAutoResizeMode(JTable.AUTO_RESIZE_NEXT_COLUMN);
TableColumnModel colModel=jTable1.getColumnModel();
colModel.getColumn(1).setPreferredWidth(25);    
colModel.getColumn(2).setPreferredWidth(400);

You can do this:

JPanel jp = new JPanel();
jp.add(table);

jp.setLayout(new GridLayout(1,1)); /* little trick ;) and believe me that this step is important to the automatic all columns resize! A import is also needed for using GridLayout*/
table.setAutoResizeMode(JTable.AUTO_RESIZE_ALL_COLUMNS); // this is obvius part