吉斯。(Guice. Inject into constructor)

 我有一个单身人士： 
 
public class MySingleton{
  public static getInstance(){//typical singleton getInstance
    ...
  }

  //fields
  private static volatile instance;
  @Inject
  private AnotherClassInstanceThatIWantToInjectHere anotherClassInst_BlaBla;
  private MySingleton(){
    ...
    anotherClassInst_BlaBla.doSmth();//NullPointerException happens!
    ...
  }
}
 
 这个NPE的原因是什么？ 是否因为它是构造函数或因为它是单例而发生？ 

I have a singleton:
 
public class MySingleton{
  public static getInstance(){//typical singleton getInstance
    ...
  }

  //fields
  private static volatile instance;
  @Inject
  private AnotherClassInstanceThatIWantToInjectHere anotherClassInst_BlaBla;
  private MySingleton(){
    ...
    anotherClassInst_BlaBla.doSmth();//NullPointerException happens!
    ...
  }
}
 
What is cause of this NPE? Does it happens because it is constructor or because it is singleton?

原文：https://stackoverflow.com/questions/35508930