Local variable reference and GC when passing member to new Thread as argument

Question

I am trying to understand, at a fundamental level, what will happen to the local variable being passed to the thread in the following situation. I need a cleanup action to happen on someObject which has a delete method, which calls an external API to delete the instance of someObject by its member, id .

public interface Deleteable {
    public delete() 
}

public SomeClass implements Deleteable {
    int id;
    public void delete() {
        HttpApiCall.deleteById(this.id);
    }
}

SomeClass someObject = null;
for(i = 0; i < 3; i++) {
// simple loop to illustrate problem
    someObject = new SomeClass();
    Runtime.getRuntime()
    .addShutdownHook(new Thread(someObject::delete));
}

While the program is executing, will some of the instances of SomeClass be GC'ed before the thread will be able to call delete? Will each thread receive their own copy that was newed or will the operate on the last set value of someObject ?

I read up a little bit about the volatile keyword but I am not sure it is going to help me here.

Answer 1

No. You are adding these someObject::delete method references to a collection in Runtime . Since the Runtime is still reachable, these objects too are reachable and shouldn't get GCd.