code: public static void setCacheDirectory(File cacheDirectory) {
  		if ((cacheDirectory != null) && !(cacheDirectory.isDirectory())) {
  			throw new IllegalArgumentException("Not a directory!");
  		}
  		getCacheInfo().setCacheDirectory(cacheDirectory);
  		getCacheInfo().setHasPermission(null);
  	}
docs: Sets the directory where cache files are to be created. A value of <code>null</code> indicates that the
  system-dependent default temporary-file directory is to be used. If <code>getUseCache</code> returns
  false, this value is ignored.
  
  @param cacheDirectory
  a <code>File</code> specifying a directory.
  
  @see File#createTempFile(String, String, File)
  
  @exception SecurityException
  if the security manager denies access to the directory.
  @exception IllegalArgumentException
  if <code>cacheDir</code> is non-<code>null</code> but is not a directory.
  
  @see #getCacheDirectory