Java:无法访问静态单例方法

Question

我面临一个问题。我有一个名为“ReportingService”的类，它应该是单例，并且正在扩展“CommonService”。

package MyApp.Services.ReportingService;

public class ReportingService extends CommonService {

    private static ReportingService instance = null;

    public static ReportingService getInstance() {
        if (instance == null) {
            instance = new ReportingService();
        }
        return instance;   

    }
}

并在我正在使用的其他类中访问该类

package MyApp.Services.WebReportingService;
@WebMethod(operationName = "registerUDP")
    public boolean registerUDP(
            @WebParam(name = "Friendly Name") String friendlyName,
            @WebParam(name = "Username") String username,
            @WebParam(name = "Password") String password,
            @WebParam(name = "Communication Protocol") CommunicationProtocol communicationProtocol,
            @WebParam(name = "IP Address") String ipAddress,
            @WebParam(name = "Port") int port) {

        Consumer client = new Consumer(friendlyName, username, password, communicationProtocol, ipAddress, port);

ReportingService rs = ReportingService.
        return true;

    }

在“ReportingService rs = ReportingService”中。它没有向我显示 ReportingService 类的 getInstance() 方法。我还导入了正确的包。

注意:这两个类位于不同的包中。

Answer 1

更改如下:

package MyApp.Services.ReportingService;  // FIXME - Make package names lowercase!!
                                          // FIXME - Loopy package name

public class ReportingService extends CommonService {

    private static ReportingService instance = null;

    private ReportingService() { }

    public static synchronized ReportingService getInstance() {
        if (instance == null) {
            instance = new ReportingService();
        }
        return instance;   

    }
}

和

import MyApp.Services.ReportingService.ReportingService; 

package MyApp.Services.WebReportingService ; 
                        // FIXME - Make package names lowercase!!
                        // FIXME - Loopy package names.

public class WebReportingService {

    @WebMethod(operationName = "registerUDP")
    public boolean registerUDP(
            @WebParam(name = "Friendly Name") String friendlyName,
            @WebParam(name = "Username") String username,
            @WebParam(name = "Password") String password,
            @WebParam(name = "Communication Protocol") CommunicationProtocol communicationProtocol,
            @WebParam(name = "IP Address") String ipAddress,
            @WebParam(name = "Port") int port) {

        Consumer client = new Consumer(friendlyName, username, password,
                                       communicationProtocol, ipAddress, port);

        ReportingService rs = ReportingService.getInstance();
        return true;
    }
}

注意:根据定义 Consumer 和 CommunicationProtocol 类的包，您可能需要导入它们；例如在 package 行之前添加这些行。

import some.package.Consumer;
import some.other.package.CommunicationProtocol;

注释 2:您当前选择的包名称存在一些严重的样式问题。

• 包名称应全部小写

• 您的软件包名称的前缀应该是您的公司、组织等的(反向)DNS 样式标识符；例如in.com.yourcompany...。请注意，形成此约定是有充分理由的!!

• MyApp/myapp 内容自由，不应使用

• services.reportingservice 是多余/冗长的；例如使用 services.reporting 代替

• 使用与类和包名称相同的名称是多余/冗长的

• 除非 reporting 和 webreporting 包中有很多类，否则它们可能应该折叠到一个包中。许多包含 1 或 2 个类的包没有帮助。