*	 * <p>This method is otherwise identical to	 * {@link #registerService(java.lang.String[], java.lang.Object,	 * java.util.Dictionary)}and is provided as a convenience when <tt>service</tt> will only	 * be registered under a single class name. Note that even in this case the value of the service's	 * {@link Constants#OBJECTCLASS}property will be an array of strings, rather than just a single string.	 *	 * @see #registerService(java.lang.String[], java.lang.Object,	 * java.util.Dictionary)	 */    public abstract ServiceRegistration registerService(String clazz,                            Object service,                            Dictionary properties);    /**	 * Returns a list of <tt>ServiceReference</tt> objects. This method returns a list of	 * <tt>ServiceReference</tt> objects for services which implement and were registered under	 * the specified class and match the specified filter criteria.	 *	 * <p>The list is valid at the time of the call to this method, however as the Framework is	 * a very dynamic environment, services can be modified or unregistered at anytime.	 *	 * <p><tt>filter</tt> is used to select the registered service whose	 * properties objects contain keys and values which satisfy the filter.	 * See {@link Filter}for a description of the filter string syntax.	 *	 * <p>If <tt>filter</tt> is <tt>null</tt>, all registered services	 * are considered to match the filter.	 * <p>If <tt>filter</tt> cannot be parsed, an {@link InvalidSyntaxException}will	 * be thrown with a human readable message where the filter became unparsable.	 *	 * <p>The following steps are required to select a service:	 * <ol>	 * <li>If the Java Runtime Environment supports permissions, the caller is checked for the	 * <tt>ServicePermission</tt> to get the service with the specified class.	 * If the caller does not have the correct permission, <tt>null</tt> is returned.	 * <li>If the filter string is not <tt>null</tt>, the filter string is	 * parsed and the set of registered services which satisfy the filter is	 * produced.	 * If the filter string is <tt>null</tt>, then all registered services	 * are considered to satisfy the filter.	 * <li>If <tt>clazz</tt> is not <tt>null</tt>, the set is further reduced to	 * those services which are an <tt>instanceof</tt> and were registered under the specified class.	 * The complete list of classes of which a service is an instance and which	 * were specified when the service was registered is available from the	 * service's {@link Constants#OBJECTCLASS}property.	 * <li>An array of <tt>ServiceReference</tt> to the selected services is returned.	 * </ol>	 *	 * @param clazz The class name with which the service was registered, or	 * <tt>null</tt> for all services.	 * @param filter The filter criteria.	 * @return An array of <tt>ServiceReference</tt> objects, or	 * <tt>null</tt> if no services are registered which satisfy the search.	 * @exception InvalidSyntaxException If <tt>filter</tt> contains	 * an invalid filter string which cannot be parsed.	 */    public abstract ServiceReference[] getServiceReferences(String clazz,                                String filter)    throws InvalidSyntaxException;    /**	 * Returns a <tt>ServiceReference</tt> object for a service that implements, and	 * was registered under, the specified class.	 *	 * <p>This <tt>ServiceReference</tt> object is valid at the time	 * of the call to this method, however as the Framework is a very dynamic	 * environment, services can be modified or unregistered at anytime.	 *	 * <p> This method is the same as calling {@link #getServiceReferences}with a	 * <tt>null</tt> filter string.	 * It is provided as a convenience for when the caller is interested in any service that	 * implements the specified class. <p>If multiple such services exist, the service	 * with the highest ranking (as specified in its {@link Constants#SERVICE_RANKING}property) is	 * returned.	 * <p>If there is a tie in ranking, the service with the lowest	 * service ID (as specified in its {@link Constants#SERVICE_ID}property); that is,	 * the service that was registered first is returned.	 *	 * @param clazz The class name with which the service was registered.	 * @return A <tt>ServiceReference</tt> object, or <tt>null</tt>	 * if no services are registered which implement the named class.	 * @see #getServiceReferences	 */    public abstract ServiceReference getServiceReference(String clazz);    /**	 * Returns the specified service object for a service.	 * <p>A bundle's use of a service is tracked by the bundle's use	 * count of that service. Each time a service's service object is returned by	 * {@link #getService}the context bundle's use count for that service	 * is incremented by one. Each time the service is released by	 * {@link #ungetService}the context bundle's use count for that service is decremented by one.	 * <p>When a bundle's use count for a service drops to zero, the bundle should no longer use that service.	 * See {@link #getBundle}for a definition of context bundle.	 *	 * <p>This method will always return <tt>null</tt> when the	 * service associated with this <tt>reference</tt> has been unregistered.	 *	 * <p>The following steps are required to get the service object:	 * <ol>	 * <li>If the service has been unregistered, <tt>null</tt> is returned.	 * <li>The context bundle's use count for this service is incremented by one.	 * <li>If the context bundle's use count for the service is currently one and	 * the service was registered with an object implementing the <tt>ServiceFactory</tt> interface,	 * the {@link ServiceFactory#getService}method is called to create a service object	 * for the context bundle.	 * This service object is cached by the Framework.	 * While the context bundle's use count for the service is greater than	 * zero, subsequent calls to get the services's service object for the	 * context bundle will return the cached service object.	 * <br>If the service object returned by the <tt>ServiceFactory</tt> object	 * is not an <tt>instanceof</tt> all the classes named when the service was registered or	 * the <tt>ServiceFactory</tt> object throws an exception, <tt>null</tt> is returned and a	 * Framework event of type {@link FrameworkEvent#ERROR}is broadcast.	 * <li>The service object for the service is returned.	 * </ol>	 *	 * @param reference A reference to the service.	 * @return A service object for the service associated with <tt>reference</tt>,	 * or <tt>null</tt> if the service is not registered or does not implement the classes	 * under which it was registered in the case of a Service Factory.	 * @exception java.lang.SecurityException If the caller does not have	 * the <tt>ServicePermission</tt> to get the service using at least one of the named classes	 * the service was registered under, and the Java Runtime Environment supports permissions.	 * @exception java.lang.IllegalStateException If the context bundle has stopped.	 * @see #ungetService	 * @see ServiceFactory	 */    public abstract Object getService(ServiceReference reference);    /**	 * Releases the service object referenced by the specified <tt>ServiceReference</tt> object.	 * If the context bundle's use count for the service is zero, this method	 * returns <tt>false</tt>. Otherwise, the context bundle's use count	 * for the service is decremented by one.	 * See {@link #getBundle}for a definition of context bundle.	 *	 * <p>The service's service object should no longer be used and all references to it	 * should be destroyed when a bundle's use count for the service drops to zero.	 *	 * <p>The following steps are required to unget the service object:	 * <ol>	 * <li>If the context bundle's use count for the service is zero or	 * the service has been unregistered, <tt>false</tt> is returned.	 * <li>The context bundle's use count for this service is decremented by one.	 * <li>If the context bundle's use count for the service is currently zero and	 * the service was registered with a <tt>ServiceFactory</tt> object, the	 * {@link ServiceFactory#ungetService}method is called to release the service object	 * for the context bundle.	 * <li><tt>true</tt> is returned.	 * </ol>	 *	 * @param reference A reference to the service to be released.	 * @return <tt>false</tt> if the context bundle's use count for the	 * service is zero or if the service has been unregistered; <tt>true</tt> otherwise.	 * @exception java.lang.IllegalStateException If the context bundle has stopped.	 * @see #getService	 * @see ServiceFactory	 */    public abstract boolean ungetService(ServiceReference reference);    /**	 * Creates a <tt>File</tt> object for a file in the	 * persistent storage area provided for the bundle by the Framework.	 * This method will return <tt>null</tt> if the platform does not	 * have file system support.	 *	 * <p>A <tt>File</tt> object for the base directory of the	 * persistent storage area provided for the context bundle by the Framework	 * can be obtained by calling this method with an empty string (" ")	 * as <tt>filename</tt>.	 * See {@link #getBundle}for a definition of context bundle.	 *	 * <p>If the Java Runtime Environment supports permissions,	 * the Framework will ensure that the bundle has the <tt>java.io.FilePermission</tt> with actions	 * <tt>read</tt>, <tt>write</tt>, <tt>delete</tt> for all files (recursively) in the	 * persistent storage area provided for the context bundle.	 *	 * @param filename A relative name to the file to be accessed.	 * @return A <tt>File</tt> object that represents the requested file or	 * <tt>null</tt> if the platform does not have file system support.	 * @exception java.lang.IllegalStateException If the context bundle has stopped.	 */    public abstract File getDataFile(String filename);    /**	 * Creates a <tt>Filter</tt> object. This <tt>Filter</tt> object may be used	 * to match a <tt>ServiceReference</tt> object or a <tt>Dictionary</tt> object.	 * See {@link Filter}for a description of the filter string syntax.	 *	 * <p>If the filter cannot be parsed, an {@link InvalidSyntaxException}will be thrown	 * with a human readable message where the filter became unparsable.	 *	 * @param filter The filter string.	 * @return A <tt>Filter</tt> object encapsulating the filter string.	 * @exception InvalidSyntaxException If <tt>filter</tt> contains	 * an invalid filter string that cannot be parsed.	 * @exception NullPointerException If <tt>filter</tt> is null.	 *	 * @since 1.1	 */    public abstract Filter createFilter(String filter)    throws InvalidSyntaxException;}