How To Initialize Variable Only Once

I'm working on a program where the user inputs song information (name, artist, filesize, duration) which is stored in a database. Once the user adds a song, the details should be stored in the first empty song slot (4 song slots total) and then taken back to the menu interface.

What I'm having trouble with is that I can add the first song fine (song1), but when I try to add another song, the information entered into song1 is gone. I've worked out that this is because every time I call upon the addNewSong() method, I'm creating four Song objects that are brand new with the line:

Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Song song4 = new Song();

How to fix this problem is where I'm stuck because if I move these lines elsewhere, I get a 'cannot find symbol - variable song1' error.

Here is my code:

public class SongDatabase {
Scanner console = new Scanner(System.in);
public void addNewSong() {
Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Song song4 = new Song();
if (song1.isEmpty()) {

[code]....