使用字段字符串检查对象是否存在

I have a Song class(field: String name) and an Album class (initialize an Arraylist fill with Song objects), I am adding a method (addSongAlbum(String name parameter))that first check if the song is already in the album. Everything works fine but now I want to check too if the song exist outside the album. How can I do this taking in consideration that the input of the method is a String? I have a Song class(field: String name) and an