how to get distinct value from mongodb 3.4 in java?

I was wondering how to get distinct value of mongodb table in java, using mongodb

FindIterable of Document type

My code below takes value but it is not distinct

//Clears type ComboBox items for reinserting them
typeCB.removeAllItems();
mClient = new MongoClient(connectionString);
db = mClient.getDatabase("productDB");
tableCollection = db.getCollection("Products");
whereQuery = new Document();

//Query for table collection
whereQuery.put("Product_Category",categoryCB.getSelectedItem().toString()); 
iterator = tableCollection.find(whereQuery);
cursor =  iterator.iterator();

while (cursor.hasNext())
{
    typeCB.addItem(cursor.next().getString("Product_Type"));
}