8354450: A File should be invalid if an element of its name sequence ends with a space

Reviewed-by: alanb

src/java.base/windows/classes/java/io/WinNTFileSystem.java

@@ -365,27 +365,28 @@ final class WinNTFileSystem extends FileSystem {
 
     @Override
     public boolean isInvalid(File f) {
-        if (f.getPath().indexOf('\u0000') >= 0)
+        final String pathname = f.getPath();
+
+        // Invalid if the pathname string contains a null character or if
+        // any name in the pathname's name sequence ends with a space
+        if (pathname.indexOf('\u0000') >= 0 || pathname.endsWith(" ")
+            || pathname.contains(" \\"))
             return true;
 
+        // The remaining checks are irrelevant for alternate data streams (ADS)
         if (ENABLE_ADS)
             return false;
 
-        // Invalid if there is a ":" at a position greater than 1, or if there
+        // Invalid if there is a ":" at a position other than 1, or if there
         // is a ":" at position 1 and the first character is not a letter
-        String pathname = f.getPath();
         int lastColon = pathname.lastIndexOf(":");
+        if (lastColon >= 0 &&
+            (lastColon != 1 || !isLetter(pathname.charAt(0))))
+            return true;
 
-        // Valid if there is no ":" present or if the last ":" present is
-        // at index 1 and the first character is a latter
-        if (lastColon < 0 ||
-            (lastColon == 1 && isLetter(pathname.charAt(0))))
-            return false;
-
-        // Invalid if path creation fails
-        Path path = null;
+        // Invalid if the path string cannot be converted to a Path
         try {
-            path = sun.nio.fs.DefaultFileSystemProvider.theFileSystem().getPath(pathname);
+            Path path = sun.nio.fs.DefaultFileSystemProvider.theFileSystem().getPath(pathname);
             return false;
         } catch (InvalidPathException ignored) {
         }

test/jdk/java/io/File/WinTrailingSpace.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2025, 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.
+ */
+
+import java.io.File;
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/* @test
+ * @bug 8354450
+ * @requires os.family == "windows"
+ * @summary Verify behavior for file names with a trailing space
+ * @run junit WinTrailingSpace
+ */
+public class WinTrailingSpace {
+    private static final String FILENAME_NO_TRAILING_SPACE = "foobargus";
+    private static final String FILENAME_TRAILING_SPACE = "foobargus ";
+    private static final String DIRNAME_TRAILING_SPACE = "foo \\bar\\gus";
+
+    @Test
+    public void noTrailingSpace() throws IOException {
+        File f = null;
+        try {
+            f = new File(".", FILENAME_NO_TRAILING_SPACE);
+            f.delete();
+            f.createNewFile();
+            assertTrue(f.exists());
+        } finally {
+            if (f != null)
+                f.delete();
+        }
+    }
+
+    @Test
+    public void trailingSpace() throws IOException {
+        File f = null;
+        try {
+            f = new File(".", FILENAME_TRAILING_SPACE);
+            f.delete();
+            f.createNewFile();
+            assertFalse(f.exists(), "Creation of " + f + " should have failed");
+        } catch (IOException expected) {
+        } finally {
+            if (f != null)
+                f.delete();
+        }
+    }
+
+    @Test
+    public void dirTrailingSpace() throws IOException {
+        File f = null;
+        try {
+            f = new File(".", DIRNAME_TRAILING_SPACE);
+            f.delete();
+            assertFalse(f.mkdirs(), "Creation of " + f + " should have failed");
+        } finally {
+            if (f != null)
+                f.delete();
+        }
+    }
+}