weak-references

I am a fresh new learner of Java. I'm now learning the concept of WeakReference. I came across a problem which probably looks stupid but I just wanna figure out the reason. The problem is: according to Java doc, "Weak reference objects, which do not prevent their referents from being made finalizable, finalized, and then reclaimed." So I did this small test: import java.lang.ref.WeakReference; public class A { public static void main(String[] args) { A a = new A(); WeakReference<A> wr = new WeakReference<>(a); a = null; A a1 = wr.get(); System.out.println(a); System.out.println(a1); try {

id __weak obj1 = obj0; equals id __weak obj1 = obj0; id __autoreleasing tmp = obj0; In Pro multithreading and memory management for iOS and OSX . But why the obj1 need to add to the autorelease pool, I think making a weak pointer of an object should not affect its lifetime. { NSObject* sp = [NSObject new]; NSObject* __weak wp = sp; } the above code is translate to: id sp = objc_msgSend(NSObject, "new"); id wp; objc_initWeak(&wp, sp); objc_destroyWeak(&wp); objc_storeStrong(&sp, 0); 1) obj_initWeak merely associate the weak pointer wp with the strong pointer sp to ensure that when the object

I'm trying to create a List of WeakReference s using the 4.5 generic implementation so that I can avoid type checking and casting of the WeakReference target. But, WeakReference<T> doesn't appear to support covariance, so I'm trying to establish a workaround. I'm thinking it should be doable since each T would be of a type in a particular inheritance chain. So, what I'm thinking would be along these lines: public class Animal { } public class Tiger : Animal { } public class Wolf : Animal { } var mylist = new List<WeakReference<Animal>>(); mylist.Add(new WeakReference<Animal>(new Animal()));