无限递归组合class

Question

我的程序中有一个无限递归，我在 class 中有一个字段，它的字段中有相同的 class。他们是单身人士，但这并不是他们不建造的原因。顺便说一句，我编写程序实际上无法删除相数组。

abstract class Phase{
  protected String phaseName;
  protected char[] keys;
  protected String[] commands;
  protected Phase[] phases;
  protected StringBuilder pattern;

}

class RemotePhase extends Phase{
  private static RemotePhase remotePhase;

  protected RemotePhase(){
    phaseName="Remote.";
    commands=new String[]{"Lock/unlock windows", "Toggle door", "Select dog menu"};
    setPattern();

    //Just below here starts an infinite loop
    phases=new Phase[]{FixWindows.getFixWindows(), ToggleDoor.getToggleDoor(), SelectDogPhase.getSelectDogPhase()};

  }

  public static RemotePhase getRemotePhase(){
    if(remotePhase==null){
      remotePhase=new RemotePhase();
    }
    return remotePhase;
  }
}

final class FixWindows extends Phase{
  private static FixWindows windows;
  private RemotePhase remotePhase;

  private FixWindows(){

    //execution keeps coming here as FixWindows object is never constructed
    remotePhase=RemotePhase.getRemotePhase();

  }

  public static FixWindows getFixWindows(){
    if(windows==null){
      windows=new FixWindows();
    }
    return windows;
  }
}

我已经尝试将 RemotePhase 设置为静态 class 并且 FixWindows 将其用于其成员，但是我运行在尝试覆盖抽象 class 的非静态方法时遇到了错误，并尝试在非静态上下文中从 FixWindows 调用它们。不过，我不想让它成为静态的，因为我必须再做一个 class 才能引用 RemotePhase。

尽管有任何方法可以使这项工作正常进行。谢谢

Answer 1

为什么您需要存储对单例的引用，而您始终可以通过静态 getter 访问它？这将允许从 FixWindows 延迟访问 RemotePhase，并修复您的循环依赖。因此，最干净的修复方法就是不要在 FixWindows.

的构造函数中调用 getter

final class FixWindows extends Phase{
  private static FixWindows windows;

  private FixWindows(){
      // does nothing but preventing external classes to instantiate it
  }

  public static synchronized FixWindows getFixWindows(){
    if(windows==null){
      windows=new FixWindows();
    }
    return windows;
  }

  public void methodThatRequiresTheRemotePhase(){
    doSomeStuff(RemotePhase.getRemotePhase());
  }
}

顺便提一下，我要警告你，你的代码不是线程安全的。您的 getter 应该同步。

Answer 2

这是对如何打破初始化循环的回答。然而，更好，因为您首先不需要存储对 RemotePhase 的单例引用。

你的问题是单例初始化器是相互依赖的。

打破它的一种方法是在 RemotePhase 之前分配 RemotePhase 的静态单例字段 RemotePhase 初始化完成。这将确保当初始化进行时，FixWindows 单例对象被构造，它可以找到（部分）初始化的 RemotePhase 单例对象。

所以，机会代码是这样的：

private RemotePhase() { phaseName = "Remote."; commands = new String[] { "Lock/unlock windows", "Toggle door", "Select dog menu" }; setPattern(); } private void init() { phases = new Phase[] { FixWindows.getFixWindows(), ToggleDoor.getToggleDoor(), SelectDogPhase.getSelectDogPhase() }; } public static RemotePhase getRemotePhase() { if (remotePhase == null) { remotePhase = new RemotePhase(); // assigns partially initialized object remotePhase.init(); // completes initialization } return remotePhase; }

Answer 3

你应该避免在另一个中调用构造函数。您可以改用设置器。

我为 FixWindows 展示了这个想法，您可以将同样的想法用于其他子类

abstract class Phase{
  protected String phaseName;
  protected char[] keys;
  protected String[] commands;
  protected Phase[] phases;
  protected StringBuilder pattern;

}

class RemotePhase extends Phase{
  private static RemotePhase remotePhase;

  protected RemotePhase(){
    phaseName="Remote.";
    commands=new String[]{"Lock/unlock windows", "Toggle door", "Select dog menu"};
    setPattern();

    //Just below here starts an infinite loop
    phases=new Phase[]{FixWindows.getFixWindows(this), ToggleDoor.getToggleDoor(), SelectDogPhase.getSelectDogPhase()};

  }

  public static RemotePhase getRemotePhase(){
    if(remotePhase==null){
      remotePhase=new RemotePhase();
    }
    return remotePhase;
  }
}

final class FixWindows extends Phase{
  private static FixWindows windows;
  private RemotePhase remotePhase;

  private FixWindows(){

    //execution keeps coming here as FixWindows object is never constructed
    //remotePhase=RemotePhase.getRemotePhase(); //shoud be deleted

  }

  public static FixWindows getFixWindows(remotePhase){
    if(windows==null){
      windows=new FixWindows();
      windows.setRemotePahse(remotePhase);
    }
    return windows;
  }
}

无限递归组合class

Infinite recursion composition class

java

oop

design-patterns

object-oriented-analysis

infinite-recursion