4847239: (spec) File.createTempFile() should make it clear that it doesn't create the temporary directory

src/java.base/share/classes/java/io/File.java

@@ -2110,6 +2110,13 @@ static File generateFile(String prefix, String suffix, File dir)
      * is invoked, but programmatic changes to this property are not guaranteed
      * to have any effect upon the temporary directory used by this method.
      *
+     * <p> If the {@code directory} argument is not {@code null}, then if its
+     * abstract pathname is valid and denotes an existing directory, then the
+     * file will be created in that directory; otherwise, the file will not
+     * be created and an {@code IOException} will be thrown.  In no case will
+     * a directory be created at the location specified by the {@code directory}
+     * argument.
+     *
      * @param  prefix     The prefix string to be used in generating the file's
      *                    name; must be at least three characters long
      *
@@ -2127,7 +2134,8 @@ static File generateFile(String prefix, String suffix, File dir)
      *          If the {@code prefix} argument contains fewer than three
      *          characters
      *
-     * @throws  IOException  If a file could not be created
+     * @throws  IOException
+     *          If a file could not be created
      *
      * @throws  SecurityException
      *          If a security manager exists and its {@link
@@ -2149,6 +2157,7 @@ public static File createTempFile(String prefix, String suffix,
 
         File tmpdir = (directory != null) ? directory
                                           : TempDirectory.location();
+
         @SuppressWarnings("removal")
         SecurityManager sm = System.getSecurityManager();
         File f;

test/jdk/java/io/File/createTempFile/TargetDirectory.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2021, 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 4847239
+ * @summary Verify directory parameter behavior in File.createTempFile(String,String,File)
+ */
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.AclEntry;
+import java.nio.file.attribute.AclEntryPermission;
+import java.nio.file.attribute.AclFileAttributeView;
+import java.nio.file.attribute.PosixFileAttributeView;
+import java.nio.file.attribute.PosixFilePermission;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public class TargetDirectory {
+    public static void main(String[] args) throws Exception {
+        // Target directory exists and is writable
+        Path dir = Path.of("target");
+        File target = Files.createDirectory(dir).toFile();
+        File tmp = File.createTempFile("passes", null, target);
+        if (!Files.exists(tmp.toPath())) {
+            throw new RuntimeException("Temp file not created");
+        }
+        tmp.delete();
+
+        // Make target directory read-only
+        if (Files.getFileStore(dir).supportsFileAttributeView("posix")) {
+            PosixFileAttributeView view =
+                (PosixFileAttributeView)Files.getFileAttributeView(dir,
+                    PosixFileAttributeView.class);
+            Set<PosixFilePermission> perms = new HashSet<>();
+            perms.add(PosixFilePermission.valueOf("OWNER_READ"));
+            view.setPermissions(perms);
+        } else if (Files.getFileStore(dir).supportsFileAttributeView("acl")) {
+            AclFileAttributeView view = Files.getFileAttributeView(dir,
+                AclFileAttributeView.class);
+            List<AclEntry> entries = new ArrayList<>();
+            for (AclEntry entry : view.getAcl()) {
+                Set<AclEntryPermission> perms =
+                    new HashSet<>(entry.permissions());
+                perms.remove(AclEntryPermission.ADD_FILE);
+                entries.add(AclEntry.newBuilder().setType(entry.type())
+                    .setPrincipal(entry.principal()).setPermissions(perms)
+                    .build());
+            }
+            view.setAcl(entries);
+        } else {
+            throw new RuntimeException("Required attribute view not supported");
+        }
+
+        // Target directory exists but is read-only
+        try {
+            File.createTempFile("readonly", null, target);
+            throw new RuntimeException("Exception not thrown");
+        } catch (IOException expected) {
+        } finally {
+            target.delete();
+        }
+
+        // Target directory does not exist
+        try {
+            File.createTempFile("nonexistent", null, new File("void"));
+            throw new RuntimeException("Exception not thrown");
+        } catch (IOException expected) {
+        }
+
+        // Target is a file, not a directory
+        target = Files.createFile(Path.of("file")).toFile();
+        try {
+            File.createTempFile("file", null, target);
+            throw new RuntimeException("Exception not thrown");
+        } catch (IOException expected) {
+        } finally {
+            target.delete();
+        }
+    }
+}