Beginning with JDK 1.4, two new methods have been 
  added to interface  java.Applet.AppletContext to allow applet persistence 
  across browser sessions. These methods are:
setStream(String key, InputStream stream)getStream(String key)These new methods enable the applet developer to stream data and objects from one browser session so that they can be reused in subsequent browser sessions. This provides applet persistence and makes it unnecessary to use static objects in applets for this same purpose.
setStream(key, stream) maps a key to a stream. getStream(key) 
  returns the stream mapped to the key. If the AppletContext already has a stream 
  mapped to the key when setStream(key, stream) is invoked, the mapping 
  is updated.
See the API specification for more information