Download file using selenium

in firefox, give   about:config  will give verious properties of forefox

there r d/f type of files,

rar file

doc file

exe file

create a firefox profile
FirefoxProfile profile= new FirefoxProfile();
profile.setPreference("browser.download.folderList",2);
profile.setPreference("browser.download.dir","D:\\test");
profile.setPreference("browser.helperApps.neverAsk.saveToDisk","application/msword,etc");