Can I specify in a SQLite query that a column have ANY value?

I'm trying to design a feature where the user can specify what data they get back from a query. Below are the search options to the end user.

• Players with a contract (non-null contractId)
• Players without a contract (null contractId)
• All Players (null or non-null contractId)

I'd like to make a function that can take a String and plug it into a query to return the desired data set.

public ArrayList<Player> getPlayers(String contractFilter) {
    String query = "... WHERE player.ContractId is " + contractFilter;
}

With this design, I can pass in contractFilter = "null" or contractFilter = "not null". Is there something I can pass in for the 3rd condition (null OR non-null)? Something like contractFilter = "any"?