javadoc improvements

Author: AlanBateman

make/data/jdwp/jdwp.spec

@@ -2141,14 +2141,12 @@ JDWP "Java(tm) Debug Wire Protocol"
         )
     )
     (Command IsVirtual=15
-        "Determine if a thread is scheduled by the Java virtual machine "
-        "rather than the operating system."
+        "Determine if a thread is a virtual thread."
         (Out
             (threadObject thread "The thread object ID.")
         )
         (Reply
-            (boolean isVirtual "true if the thread is scheduled by the Java virtual "
-                               "machine rather than the operating system.")
+            (boolean isVirtual "true if the thread is a virtual thread.")
         )
         (ErrorSet
             (Error INVALID_THREAD)

src/java.base/share/classes/java/lang/Thread.java

@@ -1666,17 +1666,10 @@ public static Thread startVirtualThread(Runnable task) {
     }
 
     /**
-     * Returns {@code true} if this thread scheduled by the Java virtual machine
-     * rather than the operating system.
+     * Returns {@code true} if this thread is a virtual thread. A virtual thread
+     * is scheduled by the Java virtual machine rather than the operating system.
      *
-     * <p> Threads that are scheduled by the Java virtual machine do not support
-     * all features of Thread. In particular, the Thread is not an <i>active thread</i>
-     * in its thread group and so is not enumerated or acted on by thread group
-     * operations. In addition it does not support the stop, suspend or resume
-     * methods.
-     *
-     * @return {@code true} if this thread is scheduled by the Java virtual
-     *         machine rather than the operating system
+     * @return {@code true} if this thread is a virtual thread
      *
      * @since 99
      */

src/jdk.jdi/share/classes/com/sun/jdi/ThreadReference.java

@@ -474,17 +474,18 @@ void forceEarlyReturn(Value value) throws InvalidTypeException,
                                               IncompatibleThreadStateException;
 
     /**
-     * Returns {@code true} if the thread is scheduled by the Java virtual machine
-     * rather than the operating system.
+     * Returns {@code true} if the thread is a virtual thread. A virtual
+     * thread is scheduled by the Java virtual machine rather than the
+     * operating system.
      *
-     * @return true if the thread is scheduled by the Java virtual machine rather
-     * than the operating system
+     * @return true if the thread is a virtual thread
      *
-     * @implSpec The default implementation returns false.
+     * @implSpec
+     * The default implementation throws {@code UnsupportedOperationException}.
      *
      * @since 99
      */
     default boolean isVirtual() {
-        return false;
+        throw new UnsupportedOperationException("Method not implemented");
     }
 }