2D LinkedList.contains() in Java

Question

Hey, everyone. I'm new to Java and I have 2D LinkedList like this:

LinkedList<LinkedList<String>> albums = new LinkedList<LinkedList<String>>();

Which is filled with data like so:

if (!artist.isEmpty() && !name.isEmpty()) {
    albums.add(new LinkedList<String>());
    albums.getLast().add(artist.toString());
    albums.getLast().add(name.toString());
}

But I want to make sure my list has no duplicate albums. How to check whenever my albums list already contains same pair of artist and name?

Answer 1

My suggestion would be to create a new class, called Album that looks something like this:

public class Album
{
    private String name;
    private String artist;

    public Album(String name, String artist)
    {
        this.name = name;
        this.artist = artist;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public String getArtist()
    {
        return artist;
    }

    public void setArtist(String artist)
    {
        this.artist = artist;
    }

    public boolean equals(Object o)
    {
        if (o instanceof Album)
        {
            Album that = (Album)o;
            return album.equals(that.album) && artist.equals(that.artist);
        }
        else
        {
            return false;
        }
    }

    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((album == null) ? 0 : album.hashCode());
        result = prime * result + ((artist == null) ? 0 : artist.hashCode());
        return result;
    }
}

Then you should be able to use contains() to check whether or not the album already exists in the linked list.

Answer 2

Yes, commenter is right. Create a class Album with artist and name fields and implement equals() (and hashCode()) on them. And then you can use contains() to find the duplicate. Or even consider using a Set (but only if hash code is really defined on your class, since a set is backed by a hash).