Check the presence of user friends by smack library

where con is xmpp connection,

presenceChanged is called when any friends is going offline or online 

Roster roster = con.getRoster();
roster.addRosterListener(new RosterListener() {
    // Ignored events public void entriesAdded(Collection<String> addresses) {}
    public void entriesDeleted(Collection<String> addresses) {}
    public void entriesUpdated(Collection<String> addresses) {}
    public void presenceChanged(Presence presence) {
        System.out.println("Presence changed: " + presence.getFrom() + " " + presence);
    }
});

presence.getType() return availability and presence.getMode() return away(),busy this type of options