6576763: Thread constructors throw undocumented NPE for null name

Summary: update javadoc to specify NPE as well as fix minor bug in implementation.
Reviewed-by: alanb

test/java/lang/ThreadGroup/NullThreadName.java

+/*
+ * Copyright 2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * @test
+ * @bug 6576763
+ * @summary (thread) Thread constructors throw undocumented NPE for null name
+ */
+
+/*
+ * Verify that threads constructed with a null thread name do not get added
+ * to the list of unstarted thread for a thread group. We can do this by
+ * checking that a daemon threadGroup is desroyed after its final valid thread
+ * has completed.
+ */
+
+import java.util.concurrent.CountDownLatch;
+import static java.lang.System.out;
+
+public class NullThreadName
+{
+    static CountDownLatch done = new CountDownLatch(1);
+
+    public static void main(String args[]) throws Exception {
+        ThreadGroup tg = new ThreadGroup("chegar-threads");
+        Thread goodThread = new Thread(tg, new GoodThread(), "goodThread");
+        try {
+            Thread badThread = new Thread(tg, new Runnable(){
+                @Override
+                public void run() {} }, null);
+        } catch (NullPointerException npe) {
+            out.println("OK, caught expected " + npe);
+        }
+        tg.setDaemon(true);
+        goodThread.start();
+
+        done.await();
+
+        int count = 0;
+        while (goodThread.isAlive()) {
+            /* Hold off a little to allow the thread to complete */
+            out.println("GoodThread still alive, sleeping...");
+            try { Thread.sleep(2000); }
+            catch (InterruptedException unused) {}
+
+            /* do not wait forever */
+            if (count++ > 5)
+                throw new AssertionError("GoodThread is still alive!");
+        }
+
+        if (!tg.isDestroyed()) {
+            throw new AssertionError("Failed: Thread group is not destroyed.");
+        }
+    }
+
+    static class GoodThread implements Runnable
+    {
+        @Override
+        public void run() {
+            out.println("Good Thread started...");
+            out.println("Good Thread finishing");
+            done.countDown();
+        }
+    }
+}