A phantom reference is used to determine when an object is just about to be reclaimed.
import java.lang.ref.PhantomReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
public class Main {
public static void main(String[] argv) throws Exception {
ReferenceQueue rq = new ReferenceQueue();
PhantomReference<String> pr = new PhantomReference<String>("object", rq);
while (true) {
Reference r = rq.remove();
if (r == pr) {
// about to be reclaimed.
r.clear();
}
}
}
}
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