Rename test to NulDevice and improve

test/jdk/java/nio/file/Files/NulDevice.java

@@ -0,0 +1,72 @@
+/*
+ * 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.
+ */
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import static java.nio.file.StandardOpenOption.*;
+
+/* @test
+ * @bug 8263898
+ * @summary Verify a byte can be written to the null device.
+ * @requires os.family == "windows"
+ * @run main NulDevice
+*/
+public class NulDevice {
+    public static void main(final String[] args) throws IOException {
+        System.getProperties().list(System.out);
+        System.out.println();
+        Path path = Path.of("nul");
+        try (final OutputStream os = Files.newOutputStream(path)) {
+            os.write(0x02);
+            System.out.printf("Wrote a byte to %s%n", path);
+            try (InputStream is = Files.newInputStream(path);) {
+                int aByte = is.read();
+                System.out.printf("read %d from %s%n", aByte, path);
+                if (aByte != -1) {
+                    throw new RuntimeException("Should only read -1 from NUL");
+                }
+            }
+        }
+        try (final OutputStream os = Files.newOutputStream(path, WRITE)) {
+            os.write(0x02);
+            System.out.printf("Wrote a byte to %s%n", path);
+        }
+        try (final FileChannel ch = FileChannel.open(path, CREATE,
+             TRUNCATE_EXISTING, WRITE)) {
+            byte[] bytes = "Whatever".getBytes();
+            ByteBuffer buf = ByteBuffer.allocate(2*bytes.length);
+            buf.put(bytes);
+            int nw = ch.write(buf);
+            System.out.printf("Wrote %d bytes to %s%n", nw, path);
+            if (nw != bytes.length) {
+                throw new RuntimeException("Should write " + bytes.length +
+                    " to NUL");
+            }
+        }
+    }
+}