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javax.mail
abstract public class: Folder [javadoc | source]
java.lang.Object
   javax.mail.Folder

Direct Known Subclasses:
    SimpleFolder

Folder is an abstract class that represents a folder for mail messages. Subclasses implement protocol specific Folders.

Folders can contain Messages, other Folders or both, thus providing a tree-like hierarchy rooted at the Store's default folder. (Note that some Folder implementations may not allow both Messages and other Folders in the same Folder).

The interpretation of folder names is implementation dependent. The different levels of hierarchy in a folder's full name are separated from each other by the hierarchy delimiter character.

The case-insensitive full folder name (that is, the full name relative to the default folder for a Store) INBOX is reserved to mean the "primary folder for this user on this server". Not all Stores will provide an INBOX folder, and not all users will have an INBOX folder at all times. The name INBOX is reserved to refer to this folder, when it exists, in Stores that provide it.

A Folder object obtained from a Store need not actually exist in the backend store. The exists method tests whether the folder exists or not. The create method creates a Folder.

A Folder is initially in the closed state. Certain methods are valid in this state; the documentation for those methods note this. A Folder is opened by calling its 'open' method. All Folder methods, except open, delete and renameTo, are valid in this state.

The only way to get a Folder is by invoking the getFolder method on Store, Folder, or Session, or by invoking the list or listSubscribed methods on Folder. Folder objects returned by the above methods are not cached by the Store. Thus, invoking the getFolder method with the same folder name multiple times will return distinct Folder objects. Likewise for the list and listSubscribed methods.

The Message objects within the Folder are cached by the Folder. Thus, invoking getMessage(msgno) on the same message number multiple times will return the same Message object, until an expunge is done on this Folder.

Note that a Message's message number can change within a session if the containing Folder is expunged using the expunge method. Clients that use message numbers as references to messages should be aware of this and should be prepared to deal with situation (probably by flushing out existing message number references and reloading them). Because of this complexity, it is better for clients to use Message objects as references to messages, rather than message numbers. Expunged Message objects still have to be pruned, but other Message objects in that folder are not affected by the expunge.

Nested Class Summary:
static class  Folder.TerminatorEvent   
Field Summary
protected  Store store    The parent store. 
protected  int mode    The open mode of this folder. The open mode is Folder.READ_ONLY, Folder.READ_WRITE, or -1 if not known.
    since: JavaMail - 1.1
 
public static final  int HOLDS_MESSAGES    This folder can contain messages 
public static final  int HOLDS_FOLDERS    This folder can contain other folders 
public static final  int READ_ONLY    The Folder is read only. The state and contents of this folder cannot be modified. 
public static final  int READ_WRITE    The state and contents of this folder can be modified. 
Constructor:
 protected Folder(Store store) 
    Constructor that takes a Store object.
    Parameters:
    store - the Store that holds this folder
Method from javax.mail.Folder Summary:
addConnectionListener,   addFolderListener,   addMessageChangedListener,   addMessageCountListener,   appendMessages,   close,   copyMessages,   create,   delete,   exists,   expunge,   fetch,   finalize,   getDeletedMessageCount,   getFolder,   getFullName,   getMessage,   getMessageCount,   getMessages,   getMessages,   getMessages,   getMode,   getName,   getNewMessageCount,   getParent,   getPermanentFlags,   getSeparator,   getStore,   getType,   getURLName,   getUnreadMessageCount,   hasNewMessages,   isOpen,   isSubscribed,   list,   list,   listSubscribed,   listSubscribed,   notifyConnectionListeners,   notifyFolderListeners,   notifyFolderRenamedListeners,   notifyMessageAddedListeners,   notifyMessageChangedListeners,   notifyMessageRemovedListeners,   open,   removeConnectionListener,   removeFolderListener,   removeMessageChangedListener,   removeMessageCountListener,   renameTo,   search,   search,   setFlags,   setFlags,   setFlags,   setSubscribed,   toString
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from javax.mail.Folder Detail:
 public synchronized  void addConnectionListener(ConnectionListener l) 
    Add a listener for Connection events on this Folder.

    The implementation provided here adds this listener to an internal list of ConnectionListeners.

 public synchronized  void addFolderListener(FolderListener l) 
    Add a listener for Folder events on this Folder.

    The implementation provided here adds this listener to an internal list of FolderListeners.

 public synchronized  void addMessageChangedListener(MessageChangedListener l) 
    Add a listener for MessageChanged events on this Folder.

    The implementation provided here adds this listener to an internal list of MessageChangedListeners.

 public synchronized  void addMessageCountListener(MessageCountListener l) 
    Add a listener for MessageCount events on this Folder.

    The implementation provided here adds this listener to an internal list of MessageCountListeners.

 abstract public  void appendMessages(Message[] msgs) throws MessagingException
    Append given Messages to this folder. This method can be invoked on a closed Folder. An appropriate MessageCountEvent is delivered to any MessageCountListener registered on this folder when the messages arrive in the folder.

    Folder implementations must not abort this operation if a Message in the given message array turns out to be an expunged Message.

 abstract public  void close(boolean expunge) throws MessagingException
    Close this Folder. This method is valid only on open Folders.

    A CLOSED ConnectionEvent is delivered to any ConnectionListeners registered on this Folder. Note that the folder is closed even if this method terminates abnormally by throwing a MessagingException.

 public  void copyMessages(Message[] msgs,
    Folder folder) throws MessagingException 
    Copy the specified Messages from this Folder into another Folder. This operation appends these Messages to the destination Folder. The destination Folder does not have to be opened. An appropriate MessageCountEvent is delivered to any MessageCountListener registered on the destination folder when the messages arrive in the folder.

    Note that the specified Message objects must belong to this folder. Folder implementations might be able to optimize this method by doing server-side copies.

    This implementation just invokes appendMessages() on the destination folder to append the given Messages. Specific folder implementations that support server-side copies should do so, if the destination folder's Store is the same as this folder's Store. Also, an implementation must not abort the operation if a Message in the array turns out to be an expunged Message.

 abstract public boolean create(int type) throws MessagingException
    Create this folder on the Store. When this folder is created, any folders in its path that do not exist are also created.

    If the creation is successful, a CREATED FolderEvent is delivered to any FolderListeners registered on this Folder and this Store.

 abstract public boolean delete(boolean recurse) throws MessagingException
    Delete this Folder. This method will succeed only on a closed Folder.

    The recurse flag controls whether the deletion affects subfolders or not. If true, all subfolders are deleted, then this folder itself is deleted. If false, the behaviour is dependent on the folder type and is elaborated below:

    • The folder can contain only messages: (type == HOLDS_MESSAGES).
      All messages within the folder are removed. The folder itself is then removed. An appropriate FolderEvent is generated by the Store and this folder.

    • The folder can contain only subfolders: (type == HOLDS_FOLDERS).
      If this folder is empty (does not contain any subfolders at all), it is removed. An appropriate FolderEvent is generated by the Store and this folder.
      If this folder contains any subfolders, the delete fails and returns false.

    • The folder can contain subfolders as well as messages:
      If the folder is empty (no messages or subfolders), it is removed. If the folder contains no subfolders, but only messages, then all messages are removed. The folder itself is then removed. In both the above cases, an appropriate FolderEvent is generated by the Store and this folder.

      If the folder contains subfolders there are 3 possible choices an implementation is free to do:

      1. The operation fails, irrespective of whether this folder contains messages or not. Some implementations might elect to go with this simple approach. The delete() method returns false.
      2. Any messages within the folder are removed. Subfolders are not removed. The folder itself is not removed or affected in any manner. The delete() method returns true. And the exists() method on this folder will return true indicating that this folder still exists.
        An appropriate FolderEvent is generated by the Store and this folder.
      3. Any messages within the folder are removed. Subfolders are not removed. The folder itself changes its type from HOLDS_FOLDERS | HOLDS_MESSAGES to HOLDS_FOLDERS. Thus new messages cannot be added to this folder, but new subfolders can be created underneath. The delete() method returns true indicating success. The exists() method on this folder will return true indicating that this folder still exists.
        An appropriate FolderEvent is generated by the Store and this folder.
 abstract public boolean exists() throws MessagingException
    Tests if this folder physically exists on the Store. This method can be invoked on a closed Folder.
 abstract public Message[] expunge() throws MessagingException
    Expunge (permanently remove) messages marked DELETED. Returns an array containing the expunged message objects. The getMessageNumber method on each of these message objects returns that Message's original (that is, prior to the expunge) sequence number. A MessageCountEvent containing the expunged messages is delivered to any MessageCountListeners registered on the folder.

    Expunge causes the renumbering of Message objects subsequent to the expunged messages. Clients that use message numbers as references to messages should be aware of this and should be prepared to deal with the situation (probably by flushing out existing message number caches and reloading them). Because of this complexity, it is better for clients to use Message objects as references to messages, rather than message numbers. Any expunged Messages objects still have to be pruned, but other Messages in that folder are not affected by the expunge.

    After a message is expunged, only the isExpunged and getMessageNumber methods are still valid on the corresponding Message object; other methods may throw MessageRemovedException

 public  void fetch(Message[] msgs,
    FetchProfile fp) throws MessagingException 
    Prefetch the items specified in the FetchProfile for the given Messages.

    Clients use this method to indicate that the specified items are needed en-masse for the given message range. Implementations are expected to retrieve these items for the given message range in a efficient manner. Note that this method is just a hint to the implementation to prefetch the desired items.

    An example is a client filling its header-view window with the Subject, From and X-mailer headers for all messages in the folder.

    
     Message[] msgs = folder.getMessages();
    
     FetchProfile fp = new FetchProfile();
     fp.add(FetchProfile.Item.ENVELOPE);
     fp.add("X-mailer");
     folder.fetch(msgs, fp);
     
     for (int i = 0; i < folder.getMessageCount(); i++) {
         display(msg[i].getFrom());
         display(msg[i].getSubject());
         display(msg[i].getHeader("X-mailer"));
     }
    
    

    The implementation provided here just returns without doing anything useful. Providers wanting to provide a real implementation for this method should override this method.

 protected  void finalize() throws Throwable 
 public synchronized int getDeletedMessageCount() throws MessagingException 
    Get the number of deleted messages in this Folder.

    This method can be invoked on a closed folder. However, note that for some folder implementations, getting the deleted message count can be an expensive operation involving actually opening the folder. In such cases, a provider can choose not to support this functionality in the closed state, in which case this method must return -1.

    Clients invoking this method on a closed folder must be aware that this is a potentially expensive operation. Clients must also be prepared to handle a return value of -1 in this case.

    This implementation returns -1 if this folder is closed. Else this implementation gets each Message in the folder using getMessage(int) and checks whether its DELETED flag is set. The total number of messages that have this flag set is returned.

 abstract public Folder getFolder(String name) throws MessagingException
    Return the Folder object corresponding to the given name. Note that this folder does not physically have to exist in the Store. The exists() method on a Folder indicates whether it really exists on the Store.

    In some Stores, name can be an absolute path if it starts with the hierarchy delimiter. Otherwise, it is interpreted relative to this Folder.

    Folder objects are not cached by the Store, so invoking this method on the same name multiple times will return that many distinct Folder objects.

    This method can be invoked on a closed Folder.

 abstract public String getFullName()
    Returns the full name of this Folder. If the folder resides under the root hierarchy of this Store, the returned name is relative to the root. Otherwise an absolute name, starting with the hierarchy delimiter, is returned.

    This method can be invoked on a closed Folder.

 abstract public Message getMessage(int msgnum) throws MessagingException
    Get the Message object corresponding to the given message number. A Message object's message number is the relative position of this Message in its Folder. Messages are numbered starting at 1 through the total number of message in the folder. Note that the message number for a particular Message can change during a session if other messages in the Folder are deleted and the Folder is expunged.

    Message objects are light-weight references to the actual message that get filled up on demand. Hence Folder implementations are expected to provide light-weight Message objects.

    Unlike Folder objects, repeated calls to getMessage with the same message number will return the same Message object, as long as no messages in this folder have been expunged.

    Since message numbers can change within a session if the folder is expunged , clients are advised not to use message numbers as references to messages. Use Message objects instead.

 abstract public int getMessageCount() throws MessagingException
    Get total number of messages in this Folder.

    This method can be invoked on a closed folder. However, note that for some folder implementations, getting the total message count can be an expensive operation involving actually opening the folder. In such cases, a provider can choose not to support this functionality in the closed state, in which case this method must return -1.

    Clients invoking this method on a closed folder must be aware that this is a potentially expensive operation. Clients must also be prepared to handle a return value of -1 in this case.

 public synchronized Message[] getMessages() throws MessagingException 
    Get all Message objects from this Folder. Returns an empty array if the folder is empty. Clients can use Message objects (instead of sequence numbers) as references to the messages within a folder; this method supplies the Message objects to the client. Folder implementations are expected to provide light-weight Message objects, which get filled on demand.

    This implementation invokes getMessageCount() to get the current message count and then uses getMessage() to get Message objects from 1 till the message count.

 public synchronized Message[] getMessages(int[] msgnums) throws MessagingException 
    Get the Message objects for message numbers specified in the array.

    Message objects are light-weight references to the actual message that get filled up on demand. Hence Folder implementations are expected to provide light-weight Message objects.

    This implementation uses getMessage(index) to obtain the required Message objects. Note that the returned array must contain msgnums.length Message objects

 public synchronized Message[] getMessages(int start,
    int end) throws MessagingException 
    Get the Message objects for message numbers ranging from start through end, both start and end inclusive. Note that message numbers start at 1, not 0.

    Message objects are light-weight references to the actual message that get filled up on demand. Hence Folder implementations are expected to provide light-weight Message objects.

    This implementation uses getMessage(index) to obtain the required Message objects. Note that the returned array must contain (end-start+1) Message objects.

 public int getMode() 
    Return the open mode of this folder. Returns Folder.READ_ONLY, Folder.READ_WRITE, or -1 if the open mode is not known (usually only because an older Folder provider has not been updated to use this new method).
 abstract public String getName()
    Returns the name of this Folder.

    This method can be invoked on a closed Folder.

 public synchronized int getNewMessageCount() throws MessagingException 
    Get the number of new messages in this Folder.

    This method can be invoked on a closed folder. However, note that for some folder implementations, getting the new message count can be an expensive operation involving actually opening the folder. In such cases, a provider can choose not to support this functionality in the closed state, in which case this method must return -1.

    Clients invoking this method on a closed folder must be aware that this is a potentially expensive operation. Clients must also be prepared to handle a return value of -1 in this case.

    This implementation returns -1 if this folder is closed. Else this implementation gets each Message in the folder using getMessage(int) and checks whether its RECENT flag is set. The total number of messages that have this flag set is returned.

 abstract public Folder getParent() throws MessagingException
    Returns the parent folder of this folder. This method can be invoked on a closed Folder. If this folder is the top of a folder hierarchy, this method returns null.

    Note that since Folder objects are not cached, invoking this method returns a new distinct Folder object.

 abstract public Flags getPermanentFlags()
    Get the permanent flags supported by this Folder. Returns a Flags object that contains all the flags supported.

    The special flag Flags.USER indicates that this Folder supports arbitrary user-defined flags.

    The supported permanent flags for a folder may not be available until the folder is opened.

 abstract public char getSeparator() throws MessagingException
    Return the delimiter character that separates this Folder's pathname from the names of immediate subfolders. This method can be invoked on a closed Folder.
 public Store getStore() 
    Returns the Store that owns this Folder object. This method can be invoked on a closed Folder.
 abstract public int getType() throws MessagingException
    Returns the type of this Folder, that is, whether this folder can hold messages or subfolders or both. The returned value is an integer bitfield with the appropriate bits set. This method can be invoked on a closed folder.
 public URLName getURLName() throws MessagingException 
    Return a URLName representing this folder. The returned URLName does not include the password used to access the store.
 public synchronized int getUnreadMessageCount() throws MessagingException 
    Get the total number of unread messages in this Folder.

    This method can be invoked on a closed folder. However, note that for some folder implementations, getting the unread message count can be an expensive operation involving actually opening the folder. In such cases, a provider can choose not to support this functionality in the closed state, in which case this method must return -1.

    Clients invoking this method on a closed folder must be aware that this is a potentially expensive operation. Clients must also be prepared to handle a return value of -1 in this case.

    This implementation returns -1 if this folder is closed. Else this implementation gets each Message in the folder using getMessage(int) and checks whether its SEEN flag is set. The total number of messages that do not have this flag set is returned.

 abstract public boolean hasNewMessages() throws MessagingException
    Returns true if this Folder has new messages since the last time this indication was reset. When this indication is set or reset depends on the Folder implementation (and in the case of IMAP, depends on the server). This method can be used to implement a lightweight "check for new mail" operation on a Folder without opening it. (For example, a thread that monitors a mailbox and flags when it has new mail.) This method should indicate whether any messages in the Folder have the RECENT flag set.

    Note that this is not an incremental check for new mail, i.e., it cannot be used to determine whether any new messages have arrived since the last time this method was invoked. To implement incremental checks, the Folder needs to be opened.

    This method can be invoked on a closed Folder that can contain Messages.

 abstract public boolean isOpen()
    Indicates whether this Folder is in the 'open' state.
 public boolean isSubscribed() 
    Returns true if this Folder is subscribed.

    This method can be invoked on a closed Folder.

    The default implementation provided here just returns true.

 public Folder[] list() throws MessagingException 
    Convenience method that returns the list of folders under this Folder. This method just calls the list(String pattern) method with "%" as the match pattern. This method can be invoked on a closed Folder.
 abstract public Folder[] list(String pattern) throws MessagingException
    Returns a list of Folders belonging to this Folder's namespace that match the specified pattern. Patterns may contain the wildcard characters "%", which matches any character except hierarchy delimiters, and "*", which matches any character.

    As an example, given the folder hierarchy:

       Personal/
          Finance/
             Stocks
             Bonus
             StockOptions
          Jokes
    
    list("*") on "Personal" will return the whole hierarchy.
    list("%") on "Personal" will return "Finance" and "Jokes".
    list("Jokes") on "Personal" will return "Jokes".
    list("Stock*") on "Finance" will return "Stocks" and "StockOptions".

    Folder objects are not cached by the Store, so invoking this method on the same pattern multiple times will return that many distinct Folder objects.

    This method can be invoked on a closed Folder.

 public Folder[] listSubscribed() throws MessagingException 
    Convenience method that returns the list of subscribed folders under this Folder. This method just calls the listSubscribed(String pattern) method with "%" as the match pattern. This method can be invoked on a closed Folder.
 public Folder[] listSubscribed(String pattern) throws MessagingException 
    Returns a list of subscribed Folders belonging to this Folder's namespace that match the specified pattern. If the folder does not support subscription, this method should resolve to list. (The default implementation provided here, does just this). The pattern can contain wildcards as for list.

    Note that, at a given level of the folder hierarchy, a particular folder may not be subscribed, but folders underneath that folder in the folder hierarchy may be subscribed. In order to allow walking the folder hierarchy, such unsubscribed folders may be returned, indicating that a folder lower in the hierarchy is subscribed. The isSubscribed method on a folder will tell whether any particular folder is actually subscribed.

    Folder objects are not cached by the Store, so invoking this method on the same pattern multiple times will return that many distinct Folder objects.

    This method can be invoked on a closed Folder.

 protected  void notifyConnectionListeners(int type) 
    Notify all ConnectionListeners. Folder implementations are expected to use this method to broadcast connection events.

    The provided implementation queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the registered ConnectionListeners. Note that the event dispatching occurs in a separate thread, thus avoiding potential deadlock problems.

 protected  void notifyFolderListeners(int type) 
    Notify all FolderListeners registered on this Folder and this folder's Store. Folder implementations are expected to use this method to broadcast Folder events.

    The implementation provided here queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the FolderListeners registered on this folder. The implementation also invokes notifyFolderListeners on this folder's Store to notify any FolderListeners registered on the store.

 protected  void notifyFolderRenamedListeners(Folder folder) 
    Notify all FolderListeners registered on this Folder and this folder's Store about the renaming of this folder. Folder implementations are expected to use this method to broadcast Folder events indicating the renaming of folders.

    The implementation provided here queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the FolderListeners registered on this folder. The implementation also invokes notifyFolderRenamedListeners on this folder's Store to notify any FolderListeners registered on the store.

 protected  void notifyMessageAddedListeners(Message[] msgs) 
    Notify all MessageCountListeners about the addition of messages into this folder. Folder implementations are expected to use this method to broadcast MessageCount events for indicating arrival of new messages.

    The provided implementation queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the registered MessageCountListeners. Note that the event dispatching occurs in a separate thread, thus avoiding potential deadlock problems.

 protected  void notifyMessageChangedListeners(int type,
    Message msg) 
    Notify all MessageChangedListeners. Folder implementations are expected to use this method to broadcast MessageChanged events.

    The provided implementation queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to registered MessageChangedListeners. Note that the event dispatching occurs in a separate thread, thus avoiding potential deadlock problems.

 protected  void notifyMessageRemovedListeners(boolean removed,
    Message[] msgs) 
    Notify all MessageCountListeners about the removal of messages from this Folder. Folder implementations are expected to use this method to broadcast MessageCount events indicating removal of messages.

    The provided implementation queues the event into an internal event queue. An event dispatcher thread dequeues events from the queue and dispatches them to the registered MessageCountListeners. Note that the event dispatching occurs in a separate thread, thus avoiding potential deadlock problems.

 abstract public  void open(int mode) throws MessagingException
    Open this Folder. This method is valid only on Folders that can contain Messages and that are closed.

    If this folder is opened successfully, an OPENED ConnectionEvent is delivered to any ConnectionListeners registered on this Folder.

    The effect of opening multiple connections to the same folder on a specifc Store is implementation dependent. Some implementations allow multiple readers, but only one writer. Others allow multiple writers as well as readers.

 public synchronized  void removeConnectionListener(ConnectionListener l) 
    Remove a Connection event listener.

    The implementation provided here removes this listener from the internal list of ConnectionListeners.

 public synchronized  void removeFolderListener(FolderListener l) 
    Remove a Folder event listener.

    The implementation provided here removes this listener from the internal list of FolderListeners.

 public synchronized  void removeMessageChangedListener(MessageChangedListener l) 
    Remove a MessageChanged listener.

    The implementation provided here removes this listener from the internal list of MessageChangedListeners.

 public synchronized  void removeMessageCountListener(MessageCountListener l) 
    Remove a MessageCount listener.

    The implementation provided here removes this listener from the internal list of MessageCountListeners.

 abstract public boolean renameTo(Folder f) throws MessagingException
    Rename this Folder. This method will succeed only on a closed Folder.

    If the rename is successful, a RENAMED FolderEvent is delivered to FolderListeners registered on this folder and its containing Store.

 public Message[] search(SearchTerm term) throws MessagingException 
    Search this Folder for messages matching the specified search criterion. Returns an array containing the matching messages . Returns an empty array if no matches were found.

    This implementation invokes search(term, getMessages()), to apply the search over all the messages in this folder. Providers that can implement server-side searching might want to override this method to provide a more efficient implementation.

 public Message[] search(SearchTerm term,
    Message[] msgs) throws MessagingException 
    Search the given array of messages for those that match the specified search criterion. Returns an array containing the matching messages. Returns an empty array if no matches were found.

    Note that the specified Message objects must belong to this folder.

    This implementation iterates through the given array of messages, and applies the search criterion on each message by calling its match() method with the given term. The messages that succeed in the match are returned. Providers that can implement server-side searching might want to override this method to provide a more efficient implementation. If the search term is too complex or contains user-defined terms that cannot be executed on the server, providers may elect to either throw a SearchException or degenerate to client-side searching by calling super.search() to invoke this implementation.

 public synchronized  void setFlags(Message[] msgs,
    Flags flag,
    boolean value) throws MessagingException 
    Set the specified flags on the messages specified in the array. This will result in appropriate MessageChangedEvents being delivered to any MessageChangedListener registered on this Message's containing folder.

    Note that the specified Message objects must belong to this folder. Certain Folder implementations can optimize the operation of setting Flags for a group of messages, so clients might want to use this method, rather than invoking Message.setFlags for each Message.

    This implementation degenerates to invoking setFlags() on each Message object. Specific Folder implementations that can optimize this case should do so. Also, an implementation must not abort the operation if a Message in the array turns out to be an expunged Message.

 public synchronized  void setFlags(int[] msgnums,
    Flags flag,
    boolean value) throws MessagingException 
    Set the specified flags on the messages whose message numbers are in the array. This will result in appropriate MessageChangedEvents being delivered to any MessageChangedListener registered on this Message's containing folder.

    Certain Folder implementations can optimize the operation of setting Flags for a group of messages, so clients might want to use this method, rather than invoking Message.setFlags for each Message.

    The default implementation uses getMessage(int) to get each Message object and then invokes setFlags on that object to set the flags. Specific Folder implementations that can optimize this case should do so. Also, an implementation must not abort the operation if a message number refers to an expunged message.

 public synchronized  void setFlags(int start,
    int end,
    Flags flag,
    boolean value) throws MessagingException 
    Set the specified flags on the messages numbered from start through end, both start and end inclusive. Note that message numbers start at 1, not 0. This will result in appropriate MessageChangedEvents being delivered to any MessageChangedListener registered on this Message's containing folder.

    Certain Folder implementations can optimize the operation of setting Flags for a group of messages, so clients might want to use this method, rather than invoking Message.setFlags for each Message.

    The default implementation uses getMessage(int) to get each Message object and then invokes setFlags on that object to set the flags. Specific Folder implementations that can optimize this case should do so. Also, an implementation must not abort the operation if a message number refers to an expunged message.

 public  void setSubscribed(boolean subscribe) throws MessagingException 
    Subscribe or unsubscribe this Folder. Not all Stores support subscription.

    This method can be invoked on a closed Folder.

    The implementation provided here just throws the MethodNotSupportedException.

 public String toString() 
    override the default toString(), it will return the String from Folder.getFullName() or if that is null, it will use the default toString() behavior.