public class JavadocDemo
{
　　/**
　　 * 这个函数的功能是返回你输入的字符串.
　　 * <p>
　　 * 用法如下：
　　 * <blockquote>
　　 * <pre>
　　 * String str = func("this is a test");
　　 * System.out.println(str);
　　 * </pre></blockquote>
　　 * @param str 输入字符串.
　　 * @return 返回字符串
　　 */
　　public static String func(String str)
　　{
　　　　return str;
　　}
}

    /**
     * Causes the current thread to wait until another thread invokes the
     * {@link java.lang.Object#notify()} method or the
     * {@link java.lang.Object#notifyAll()} method for this object, or
     * some other thread interrupts the current thread, or a certain
     * amount of real time has elapsed.
     * <p>
     * This method is similar to the {@code wait} method of one
     * argument, but it allows finer control over the amount of time to
     * wait for a notification before giving up. The amount of real time,
     * measured in nanoseconds, is given by:
     * <blockquote>
     * <pre>
     * 1000000*timeout+nanos</pre></blockquote>
     * <p>
     * In all other respects, this method does the same thing as the
     * method {@link #wait(long)} of one argument. In particular,
     * {@code wait(0, 0)} means the same thing as {@code wait(0)}.
     * <p>
     * The current thread must own this object‘s monitor. The thread
     * releases ownership of this monitor and waits until either of the
     * following two conditions has occurred:
     * <ul>
     * <li>Another thread notifies threads waiting on this object‘s monitor
     *     to wake up either through a call to the {@code notify} method
     *     or the {@code notifyAll} method.
     * <li>The timeout period, specified by {@code timeout}
     *     milliseconds plus {@code nanos} nanoseconds arguments, has
     *     elapsed.
     * </ul>
     * <p>
     * The thread then waits until it can re-obtain ownership of the
     * monitor and resumes execution.
     * <p>
     * As in the one argument version, interrupts and spurious wakeups are
     * possible, and this method should always be used in a loop:
     * <pre>
     *     synchronized (obj) {
     *         while (&lt;condition does not hold&gt;)
     *             obj.wait(timeout, nanos);
     *         ... // Perform action appropriate to condition
     *     }
     * </pre>
     * This method should only be called by a thread that is the owner
     * of this object‘s monitor. See the {@code notify} method for a
     * description of the ways in which a thread can become the owner of
     * a monitor.
     *
     * @param      timeout   the maximum time to wait in milliseconds.
     * @param      nanos      additional time, in nanoseconds range
     *                       0-999999.
     * @throws  IllegalArgumentException      if the value of timeout is
     *                      negative or the value of nanos is
     *                      not in the range 0-999999.
     * @throws  IllegalMonitorStateException  if the current thread is not
     *               the owner of this object‘s monitor.
     * @throws  InterruptedException if any thread interrupted the
     *             current thread before or while the current thread
     *             was waiting for a notification.  The <i>interrupted
     *             status</i> of the current thread is cleared when
     *             this exception is thrown.
     */
    public final void wait(long timeout, int nanos) throws InterruptedException {
        if (timeout < 0) {
            throw new IllegalArgumentException("timeout value is negative");
        }

        if (nanos < 0 || nanos > 999999) {
            throw new IllegalArgumentException(
                                "nanosecond timeout value out of range");
        }

        if (nanos > 0) {
            timeout++;
        }

        wait(timeout);
    }