8375573: JTable ignores setPreferredWidth during initial layout when AUTO_RESIZE_LAST_COLUMN is enabled

Reviewed-by: tr

src/java.desktop/share/classes/javax/swing/JTable.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -3191,9 +3191,23 @@ public class JTable extends JComponent implements TableModelListener, Scrollable
      * (maximum or minimum).
      *
      */
+
     public void doLayout() {
+        boolean prefWidthSet = false;
         TableColumn resizingColumn = getResizingColumn();
-        if (resizingColumn == null) {
+        // doLayout is called for both pack and show
+        // so if initial preferred width is set by user then
+        // it needs to be honoured even if resizingColumn
+        // is set to last column on account of
+        // AUTO_RESIZE_LAST_COLUMN autoResizeMode
+        for (int i = 0; i < columnModel.getColumnCount(); i++) {
+            if (columnModel.getColumn(i).getPreferredWidth() != 75
+                    && columnModel.getColumn(i).getWidth() == 75) {
+                prefWidthSet = true;
+                break;
+            }
+        }
+        if (resizingColumn == null || prefWidthSet) {
             setWidthsFromPreferredWidths(false);
         }
         else {

test/jdk/javax/swing/JTable/TestJTableColWidth.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8192888
+ * @key headful
+ * @summary Verifies JTable doesn't ignore setPreferredWidth during
+ *          initial layout when AUTO_RESIZE_LAST_COLUMN is enabled
+ * @run main TestJTableColWidth
+ */
+
+import javax.swing.JFrame;
+import javax.swing.JScrollPane;
+import javax.swing.JTable;
+import javax.swing.table.DefaultTableModel;
+import javax.swing.table.TableColumnModel;
+import javax.swing.SwingUtilities;
+
+public class TestJTableColWidth {
+    static JFrame frame;
+
+    public static void main(String[] args) throws Exception {
+        SwingUtilities.invokeAndWait(() -> {
+            try {
+                frame = new JFrame("JTable colwidth");
+
+                String[] cols = {"ID", "Name", "Description", "Status"};
+                Object[][] data = {{1, "Mimi", "Testing Java 25 Regression", "Pending"}};
+
+                DefaultTableModel model = new DefaultTableModel(data, cols);
+                final JTable tab = new JTable(model);
+
+                tab.getTableHeader().setReorderingAllowed(false);
+                tab.setAutoResizeMode(JTable.AUTO_RESIZE_LAST_COLUMN);
+
+                TableColumnModel columnModel = tab.getColumnModel();
+                // Defined widths
+                int[] widths = {30, 200, 100, 50};
+
+                for (int i = 0; i < widths.length; i++) {
+                    columnModel.getColumn(i).setPreferredWidth(widths[i]);
+                }
+
+                frame.add(new JScrollPane(tab));
+                frame.setSize(600, 200);
+                frame.setLocationRelativeTo(null);
+                frame.setVisible(true);
+
+                System.out.println("Actual column widths on screen:");
+                for (int i = 0; i < columnModel.getColumnCount(); i++) {
+                    System.out.println("Column " + i + ": " +
+                                        columnModel.getColumn(i).getWidth() + "px");
+                }
+                if (columnModel.getColumn(0).getWidth()
+                    == columnModel.getColumn(1).getWidth()) {
+                    throw new RuntimeException("JTable ignores setPreferredWidth during" +
+                                  " initial layout when AUTO_RESIZE_LAST_COLUMN is enabled");
+                }
+            } finally {
+                if (frame != null) {
+                    frame.dispose();
+                }
+            }
+        });
+    }
+}