现在我只是想知道为什么，prob也需要帮助。
因此，当我向列表中添加值时，它将被添加，但5分钟后它将被删除，这是可行的，但如果我添加list.size（），它仍然显示1，但里面没有值

public class Test extends Runnable {

   private ExpiringSet<User> users; //User is just my object class 

   public Test() {
       users  = new ExpiringSet<User>(5, TimeUnit.MINUTES); //Sets the users

       users.add(new User("John"));
   }

   @Override
   public void run() {
       // This will always say 1 even after i wait 1hour ive seen it has increased after a while then it said 2 
       //and there is no values in the users
       System.out.println("Size: " + users.size()); 

       //But this is empty after 5min        
       for(Iterator<User> iter = users.iterator(); iter.hasNext(); ) {
           User user = (User)iter.next();
           System.out.println("User " + user.getName());
       }
   }

}

public class ExpiringSet<E> extends ForwardingSet<E> {
   private final Set<E> setView;

   public ExpiringSet(long duration, TimeUnit unit) {
       Cache<E, Boolean> cache = CaffeineFactory.newBuilder().expireAfterAccess(duration, unit).build();
       this.setView = Collections.newSetFromMap(cache.asMap());
   }

   @Override
   protected Set<E> delegate() {
       return this.setView;
   }
}

基本上我只希望users.size（）在用户内部没有值的情况下为0。当它说1并且没有值的时候看起来很奇怪。