How to avoid duplicate values in a JComboBox?

Question

cmbMake = new JComboBox();
cmbMake.addItem("**Please Select**");
Iterator i = products.entrySet().iterator();
while (i.hasNext())
{
    Map.Entry me = (Map.Entry) i.next();
    Product p = (Product) me.getValue();

    if(!p.getMake().equals(cmbMake.getSelectedItem()))
    {
        cmbMake.addItem("" + p.getMake());
    }
}

I have a class which holds product details is there anyway to stop the same make being added to the combo box?

Answer 1

You can try this code (I added some code to yours). The code gets the values of makes and stores them in a Set collection, and then populates the combo box.

cmbMake = new JComboBox();
cmbMake.addItem("**Please Select**");

Iterator i = products.entrySet().iterator();
Set<String> uniqueMakes = new HashSet<>(); // this stores unique makes

while (i.hasNext())
{
    Map.Entry me = (Map.Entry) i.next();
    Product p = (Product) me.getValue();

    //if(! p.getMake().equals(cmbMake.getSelectedItem()))
    //{
    //  cmbMake.addItem("" + p.getMake());
    //}

    uniqueMakes.add(p.getMake());
}

System.out.println(uniqueMakes); // this prints the makes

// Add makes to the combo box
for (String make : uniqueMakes) {
    cmbMake.addItem(make);
}

Suggestions: You can use type parameters while using some of these, for example:

JComboBox<String> cmbMake = new JComboBox<>();
Iterator<Product> i = products.entrySet().iterator();

EDIT: Here are tutorials on using Set collection and using Generics.

EDIT (another way of coding the same functionality using functional-style programming):

cmbMake = new JComboBox<String>();
cmbMake.addItem("**Please Select**");
products.values()
        .map(product -> product.getMake())
        .collect(Collectors.toCollection(HashSet::new))
        .forEach(make -> cmbMake.addItem(make));