import java.util.prefs.Preferences;

public class UsingReg {

public static final String REALKEY= "com.rgagnon.foo";

public static void main(String[] args){
  new UsingReg().doit();
}

public void doit() {
  // write into HKCU\Software\Javasoft\Prefs\com.rgagnon.foo
  Preferences p = Preferences.userRoot();
  p.put(REALKEY, "bar");

  // read back from HKEY_CURRENT_USER
  System.out.println(p);
  System.out.println(p.get(REALKEY, "HKCU houston we have a problem"));

  // write into HKLM\Software\Javasoft\Prefs\com.rgagnon.foo
  p = Preferences.systemRoot();
  p.put(REALKEY, "barbar");

  // read back from HKEY_LOCAL_MACHINE
  System.out.println(p);
  System.out.println(p.get(REALKEY, "HKLM houston we have a problem"));
  }
}