The statement means that you can specify the list of properties that you want to index on as an array.
Something like this ...
private void createDatabaseIndex() {
try {
// Regular value type index
List<Expression> valueProp = new ArrayList<Expression>();
valueProp.add(Expression.property("type"));
database.createIndex(valueProp);
// Create full text search index
List<Expression> ftsProp = new ArrayList<Expression>();
ftsProp.add(Expression.property("overview"));
database.createIndex(ftsProp, IndexType.FullText, new IndexOptions("en", true));
}
catch (CouchbaseLiteException e) {
e.getStackTrace();
}
}