The AllowEventsHeader includes a list of tokens which indicates the event packages supported by the client (if sent in a request) or server (if sent in a response). In other words, a node sending an AllowEventsHeader is advertising that it can process SUBSCRIBE requests and generate NOTIFY requests for all of the event packages listed in that header.
Any node implementing one or more event packages SHOULD include an appropriate AllowEventsHeader indicating all supported events in all methods which initiate dialogs and their responses (such as INVITE) and OPTIONS responses. This information is very useful, for example, in allowing user agents to render particular interface elements appropriately according to whether the events required to implement the features they represent are supported by the appropriate nodes.
Note that "Allow-Events" headers MUST NOT be inserted by proxies.
eventType- the String defining the method supported in this AllowEventsHeader
java.text.ParseExceptionwhich signals that an error has been reached unexpectedly while parsing the Strings defining the eventType supported