This abstract class defines an API for low-level caching of network resources retrieved through the URL and URLConnection classes. This class is intended for use by URLStreamHandler implementations, not by casual users of the java.net package. Clients that wish to enable local caching should register a ResponseCache implementation with setDefault( ) and enable caching with URLConnection.setDefaultUseCaches( ).

The static geTDefault( ) and setDefault( ) methods query and set a ResponseCache for the system. If there is a ResponseCache installed, protocol handlers should call put( ) to offer a network resource to the cache. If the cache is interested, it returns a CacheRequest object into which the URLStreamHandler can write its data. A URLStreamHandler that wants to query the cache should call get( ). If the ResponseCache holds a cached copy of the requested resource, it returns a CacheResponse from which the URLStreamHandler can read the resource.

public abstract class ResponseCache {
// Public Constructors
     public ResponseCache( );  
// Public Class Methods
     public static ResponseCache getDefault( );      synchronized
     public static void setDefault(ResponseCache responseCache);    synchronized
// Public Instance Methods
     public abstract CacheResponse get(URI uri, String rqstMethod, 
java.util.Map<String,java.util.List<String>> rqstHeaders) 
        throws java.io.IOException;
     public abstract CacheRequest put(URI uri, URLConnection conn) 
        throws java.io.IOException;  
}