java - 如何避免 JComboBox 中的重复值？

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());
    }
}

我有一个包含产品详细信息的类，是否可以阻止将相同品牌添加到组合框中？

Answer 1

您可以试试这段代码(我在您的代码中添加了一些代码)。代码获取 makes 的值并将它们存储在 Set 中集合，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时使用类型参数，例如:

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

编辑:这里是关于 using Set collection 的教程和 using Generics .

编辑(使用函数式编程编写相同功能的另一种方法):

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