java - 在 Java 中的方法之间使用相同的对象实例

Question

我今天早些时候问了一个类似的问题并选择了一个答案，但我认为我的措辞不正确，无法得到我需要的答案。请考虑下面的代码..

public class ClassA {

    private Main main;
    Object obj = new Object;

    public void setMain(Main main) {
        this.main = main;
    }
    methodA() {  //called first
        obj.someFunction();
        main.someFunction();
    }
    methodB() {  //called second
        obj.someOtherFunction();
    }
}

我的程序中的对象“obj”是一个 OAuthService 实例，必须在整个过程中使用它，而无需“重新创建”它(相同的哈希值，没有更改)。

我用方法A调用“obj”，在main中调用函数，然后在方法B中再次调用“obj”。当我从 methodA 和 methodB 打印 hashCodes 时，我得到不同的结果，告诉我它正在“重新创建”实例。

如何避免这种情况？

我确信对于更有经验的程序员来说，这可能听起来像是一个愚蠢的问题，但我才刚刚开始编程，而且我在任何地方都找不到我需要的解决方案。任何帮助将不胜感激。

实际代码

“AuthController”类，其中“obj”是 OAuth10aService“服务”，methodA 是“handlePinButton”，methodB 是“handlePinSubmit”。我尝试过使用另外两个用于 java 的 OAuth 库进行身份验证，并遇到类似的错误。 Scribe-java 是我现在使用的，

public class AuthController {

private final String CONSUMER_KEY = "asdbfsdfbsdf";
private final String CONSUMER_SECRET = "asdfsdbvbvfsdsd";


final OAuth10aService service = new ServiceBuilder()
        .apiKey(CONSUMER_KEY)
        .apiSecret(CONSUMER_SECRET)
        .build(TwitterApi.instance());
final Token requestToken = service.getRequestToken();

Desktop desktop = Desktop.getDesktop();

@FXML
public JFXTextField enterPinField;
@FXML
public JFXButton submitPinButton;

private Main main;

public void setMain(Main main) {
    this.main = main;
}

public void handlePinButton() throws Exception { //call first

    System.out.println(service.hashCode());
    String authUrl = service.getAuthorizationUrl(requestToken);
    desktop.browse(new URI(authUrl));
    main.secondWindow();

}

public void handlePinSubmit() throws Exception { //call second

    System.out.println(service.hashCode());

    Verifier verifier = new Verifier(enterPinField.getText());
    System.out.println(verifier);

    Token accessToken = service.getAccessToken(requestToken, verifier);
    System.out.println(accessToken);


  }
}

输出以下内容:

  WARNING: Loading FXML document with JavaFX API of version 8.0.65 by JavaFX runtime of version 8.0.51
722985119
Feb 12, 2016 4:47:05 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 8.0.65 by JavaFX runtime of version 8.0.51
960671619
com.github.scribejava.core.model.Verifier@2546ed3b
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8390)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3758)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3486)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2495)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:350)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$350(GlassViewEventHandler.java:385)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$166/1959217067.get(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:384)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:927)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1767)
    ... 46 more
Caused by: com.github.scribejava.core.exceptions.OAuthException: Response body is incorrect. Can't extract token and secret from this: 'Error processing your OAuth request: Invalid oauth_verifier parameter'
    at com.github.scribejava.core.extractors.TokenExtractorImpl.extract(TokenExtractorImpl.java:39)
    at com.github.scribejava.core.extractors.TokenExtractorImpl.extract(TokenExtractorImpl.java:29)
    at com.github.scribejava.core.oauth.OAuth10aService.getAccessToken(OAuth10aService.java:86)
    at controller.AuthController.handlePinSubmit(AuthController.java:65)
    ... 56 more

Answer 1

使用单例模式。像下面这样定义你的类，当你想获取唯一一个对象时，调用 MyClass.getInstance() 方法而不是 new MyClass() 。

public class MyClass
{
    /**
     * Create the only one instance of this class.
     */
    private static final MyClass sInstane = new MyClass();

    /**
     * This is the only one constructor in this class.
     * Because this is 'private', no others can create
     * instances of this class.
     */
    private MyClass()
    {
    }

    /**
     * Get the only one instance of this class.
     */
    public static MyClass getInstance()
    {
        return sInstance;
    }
}