Previous assignee

I want to make some operations in java, when assignee of a task is changed.
I can get an assignee from issue like:

public void onIssueEvent(IssueEvent issueEvent) {
    Long eventTypeId = issueEvent.getEventTypeId();
    Long issue = issueEvent.getIssue().getAssigneeId();

but it return only the current one. Is there any way to get the previous one?

You want . Basically once you know the issue - you can look up the history of a specific field.