Class IMAPFolder

app/src/main/java/com/sun/mail/imap/IMAPFolder.java:158–4128

 */

public class IMAPFolder extends Folder implements UIDFolder, ResponseHandler {
    
    protected volatile String fullName;	// full name
    protected String name;		// name
    protected int type;			// folder type. 
    protected char separator;		// separator
    protected Flags availableFlags; 	// available flags
    protected Flags permanentFlags; 	// permanent flags
    protected volatile boolean exists;	// whether this folder really exists ?
    protected boolean isNamespace = false; // folder is a namespace name
    protected volatile String[] attributes;// name attributes from LIST response

    protected volatile IMAPProtocol protocol; // this folder's protocol object
    protected MessageCache messageCache;// message cache
    // accessor lock for message cache
    protected final Object messageCacheLock = new Object();

    protected Hashtable<Long, IMAPMessage> uidTable; // UID->Message hashtable

    /* An IMAP delimiter is a 7bit US-ASCII character. (except NUL).
     * We use '\uffff' (a non 7bit character) to indicate that we havent
     * yet determined what the separator character is.
     * We use '\u0000' (NUL) to indicate that no separator character
     * exists, i.e., a flat hierarchy
     */
    static final protected char UNKNOWN_SEPARATOR = '\uffff';

    private volatile boolean opened = false; 	// is this folder opened ?

    /* This field tracks the state of this folder. If the folder is closed
     * due to external causes (i.e, not thru the close() method), then
     * this field will remain false. If the folder is closed thru the
     * close() method, then this field is set to true.
     *
     * If reallyClosed is false, then a FolderClosedException is
     * generated when a method is invoked on any Messaging object
     * owned by this folder. If reallyClosed is true, then the
     * IllegalStateException runtime exception is thrown.
     */
    private boolean reallyClosed = true;

    /*
     * The idleState field supports the IDLE command.
     * Normally when executing an IMAP command we hold the
     * messageCacheLock and often the folder lock (see above).
     * While executing the IDLE command we can't hold either
     * of these locks or it would prevent other threads from
     * entering Folder methods even far enough to check whether
     * an IDLE command is in progress.  We need to check before
     * issuing another command so that we can abort the IDLE
     * command.
     *
     * The idleState field is protected by the messageCacheLock.
     * The RUNNING state is the normal state and means no IDLE
     * command is in progress.  The IDLE state means we've issued
     * an IDLE command and are reading responses.  The ABORTING
     * state means we've sent the DONE continuation command and
     * are waiting for the thread running the IDLE command to