What is the lifespan of a static variable

问题

In the following code, does Nail's reference to ypaw end as soon as I exit the method someMethod or is there potential for leakage? Also, once I exit class Dog are all references to ypaw gone or does the static reference inside Nail cause troubles? Note that ypaw and mPaw are the same object and I am wondering how long the object lives in memory due to the static reference. Of course assume the Garbage Collector executes at the appropriate time.

Class Dog{

  private Paw ypaw;
  //…..

  public void someMethod(){
    Nail nail = Nail.getInstance(ypaw);
  }
}


Class Nail{
  private static Paw mPaw;

  public static Nail getInstance(Paw p){
    mPaw = p;
    return new Nail();
  }
  //…. other stuff
}

Edit

I mean to say that I have a single instance of Dog as myDog and that my single instance of Nail is through myDog. What happens to mPaw after myDog dies (i.e. is gc'ed)?

回答1:

No, a static variable lives for as long as the classloader which loaded the class does. So that's "forever" in many applications.

It's not clear what you're trying to achieve, but this code is almost certainly a bad idea.

(In general, mutable static data is a bad idea. And mutable static non-private fields are a really bad idea - you can't possibly control all access for synchronization purposes, apart from anything else.)

来源：https://stackoverflow.com/questions/23436096/what-is-the-lifespan-of-a-static-variable