All careers paths have varying degrees of stability, but from a general perspective the most stable careers are the ones that are very specialized. This is a double-edged sword in that you will be very restricted in terms of mobility depending on the specialization you elect. Also it generally is very hard to get into a specialized field as the general path is to have started with a company and then switched into the specialization because of retirement or departure by the previous specialist. Since you have 4 years of Java experience and I do not know your education background, but if you have a Masters preferably a PHD in mathematics lots of firms (And yes there are fly by night hedgefunds) are looking for programmers for algorithmic trading engines (this would be an example of a specialization – and the when the trading industry does poorly there will be a big contraction). As for SAP (depending on which of the many SAP products – I would say it would be hard for the traditional multi-million dollar ERP implementation SAP), but if you are referring to NetWeaver or their BI tools like BusinessObjects you will generally need some experience with the tool (less so for NetWeaver) or again a company willing to take a chance on you. Oracle CRM is useful but again only for a company that wants to extend the built-in features and is willing to take a chance on you.
System Administrator maybe? this job requeries less hours by day, and eventually request you to take and action over a problem.
Because you are a developer, linux system administrator, database administrator or network administrator roles are easy to take.
Think to work providing support instead providing software.