There are several setters in the FileDialog class that needs to be fixed:

void setDirectory(String dir)
void setFilenameFilter(FilenameFilter filter)
void setMode(int mode)
void setMultipleMode(boolean enable) // upcoming

Javadoc for the setFile method explicitly says:

" ... This file becomes the default file if it is set before the file dialog window is first shown ... "

Similar note should be added to the spec for other setters.