src/net/java/sip/communicator/impl/protocol/jabber/OperationSetPersistentPresenceJabberImpl.java
/**
     * Adds a subscription for the presence status of the contact
     * corresponding to the specified contactIdentifier.
     *
     * @param contactIdentifier the identifier of the contact whose status
     *   updates we are subscribing for. <p>
     * @throws IllegalArgumentException if <tt>contact</tt> is not a contact
     *   known to the underlying protocol provider
     * @throws IllegalStateException if the underlying protocol provider is
     *   not registered/signed on a public service.
     * @throws OperationFailedException with code NETWORK_FAILURE if
     *   subscribing fails due to errors experienced during network
     *   communication
     */
Adds a subscription for the presence status of the contact
corresponding to the specified contactIdentifier.

@param contactIdentifier the identifier of the contact whose status
updates we are subscribing for. 
@throws IllegalArgumentException if contact is not a contact
known to the underlying protocol provider
@throws IllegalStateException if the underlying protocol provider is
not registered/signed on a public service.
@throws OperationFailedException with code NETWORK_FAILURE if
subscribing fails due to errors experienced during network
communication
Adds a subscription for the presence status of the contact corresponding to the specified contactIdentifier . @param contactIdentifier the identifier of the contact whose status updates we are subscribing for . @throws IllegalArgumentException if contact is not a contact known to the underlying protocol provider @throws IllegalStateException if the underlying protocol provider is not registered / signed on a public service . @throws OperationFailedException with code NETWORK_FAILURE if subscribing fails due to errors experienced during network communication
public void subscribe(String contactIdentifier) throws
        IllegalArgumentException, IllegalStateException,
        OperationFailedException
    {
        assertConnected();
        ssContactList.addContact(contactIdentifier);
    }
public void subscribe ( String contactIdentifier ) throws IllegalArgumentException , IllegalStateException , OperationFailedException { assertConnected ( ) ; ssContactList . addContact ( contactIdentifier ) ; }
Adds a subscription for the presence status of the contact
 corresponding to the specified contactIdentifier.
Adds a subscription for the presence status of the contact corresponding to the specified contactIdentifier .