set column-width in a JTable

javax.swing.table.JTable

JTable table = new JTable(10, 20);
 
// turn off autoresizing, or else all columns are equal wide:
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
 
// set first column on 100 pixel width:
final int INDEX_COLUMN1 = 0;
TableColumn col = table.getColumnModel().getColumn(INDEX_COLUMN1);
col.setPreferredWidth(100);