无法从接口实例化类

Question

我在构建的应用程序中有以下界面：

package sistemata;
public interface PaymentgatewayAdapter
{   
    public String postPayment(String a);
}

下面的类实现了它：

public class PaypalAdapter implements PaymentgatewayAdapter
{
    public String postPayment(String a)
    {
        String payAmount;
        String transactionOutcome;
        String response;
        payAmount = a;
        Paypal_sim systemGN = new Paypal_sim();
        System.out.println("v adaptera" + a);
        //Simulerar att data skickas till externa systemet
        response = systemGN.transferSaleData(payAmount);
        if (response == "OK")
        {
            transactionOutcome = "OK";
        }
        else
        {
            transactionOutcome = "Invalid data sent to MasterCard.";
        }
        return transactionOutcome;
        //------------------------------
    }
}

还有第二个几乎相同的类称为Payson，但它没有被使用。此接口是ServicesFactory的一部分：

package sistemata;
public class ServicesFactory
{
    private static ServicesFactory instance;
    private PaymentgatewayAdapter paymentAdapter;
    private String className2;
    public static synchronized ServicesFactory getInstance()
    {
        instance = new ServicesFactory();
        return instance;
    }

    public PaymentgatewayAdapter getPaymentAdapter(String className2) 
    {
        this.className2 = className2;
        if (paymentAdapter == null)
        {
            try
            {
                paymentAdapter = (PaymentgatewayAdapter)
                        Class.forName(className2).newInstance();
            }
            catch (Exception e)
            {
                System.out.println("ERROR: Cannot instantiate: " +
                        className2 + ".");
                e.printStackTrace();
                System.exit(1);
            }
        }
        return paymentAdapter;  
    }
}

getPaymentAdapter Account类中调用的方法，如下所示：

else if (paymentMethod == 0)
{
    System.out.println("The payment method is PayPal INC");
    String className = "PaypalAdapter";
    paymentAdapter = ServicesFactory.getInstance().getPaymentAdapter(className);
}

每当我打电话：

paymentAdapter = ServicesFactory.getInstance().getPaymentAdapter(className);

我收到抛出的错误System.out.println("ERROR: Cannot instantiate:.无论我尝试什么，我都无法解决这个问题，也找不到解决方案。我将感谢对此代码的一些帮助，甚至是硬编码的建议。

java.lang.ClassNotFoundException: PaymentgatewayAdapter
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at sistemata.ServicesFactory.getPaymentAdapter(ServicesFactory.java:26)
    at sistemata.Account.makePayment(Account.java:56)
    at sistemata.MainSystem.main(MainSystem.java:71)

Answer 1

您是否忘记了此行中的软件包名称？

String className = "PaypalAdapter";

应该是

String className = "sistemata.x.y.z.PaypalAdapter";

Answer 2

传递给

Class.forName()的类名必须是完全限定的类名，包括包。尝试使用"系统。贝宝适配器"。