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());
    }
}

我有一个保存产品详细信息的类，是否有同样的方法来阻止将同一品牌添加到组合框中？

Answer 1

假设make是String，只需创建一个包含所有不同值的集合，然后将它们添加到ComboBox：

Set<String> productMakes = new HashSet<String>();
for (Map.Entry<KeyClass, Product> productEntry: products.entrySet()) {
    productMakes.add(productEntry.getValue().getMake());
}

// How about sorting the items before adding them to the ComboBox?
List<String> sortedProductMakes = new ArrayList<String>(productMakes);
java.util.Collections.sort(sortedProductMakes);

for (String productMake : sortedProductMakes ) {
    cmbMake.addItem(productMake);
}

Answer 2

您可以尝试使用此代码（我在您的代码中添加了一些代码）。该代码获取 makes 的值并将其存储在Set集合中，然后填充组合框。

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);
}

建议：您可以在使用其中一些参数时使用类型参数，例如：

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

编辑：这是有关using Set collection和using Generics的教程。

EDIT（使用函数式编程对相同功能进行编码的另一种方式）：

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

Answer 3

将所有值添加到Set并对其进行迭代：

 for(Object o : new HashSet<>(products.values())){
        Product p = (Product) o.getValue();
        if(!p.getMake().equals(cmbMake.getSelectedItem()))   {
            cmbMake.addItem("" + p.getMake());
        }
 }

Answer 4

尝试此代码，

cmbMake = new JComboBox();
    cmbMake.addItem("**Please Select**");
    Map products = null;
    Iterator i = products.entrySet().iterator();

        while (i.hasNext()) {
            Map.Entry me = (Map.Entry) i.next();
            Product p = (Product) me.getValue();
            Set<String> productSet = new HashSet<String>();
            productSet.add(p.getMake());
            if (!p.getMake().equals(cmbMake.getSelectedItem())) {
                if (productSet.size() > 0) {
                    productSet.forEach(action -> {
                        cmbMake.addItem("" + action);
                    });
                }

            }
        }

如何停止JComboBox中的重复？

4 个答案: