Guava CacheBuilder: imply additional conditions to entity removal

问题

I want: Remove entity when both conditions are true

• timeout expired
• some external conditions are true

Question: How should I imply additional removal conditions besides timeout? Or how can I restore entity from removal listener (see code below)?

My code (which already remove based on timeout only):

LoadingCache<String, Integer> ints = CacheBuilder.newBuilder()
        .maximumSize(10000)
        .expireAfterAccess(ACCESS_TIMEOUT, TimeUnit.MILLISECONDS)
        .removalListener(
                new RemovalListener() {                       
                    public void onRemoval(RemovalNotification notification) {
                        if (notification.getCause() == RemovalCause.EXPIRED) {
                            if (!isExternalCondition()) {
                               //IS IT POSSIBLE TO RESTORE?
                              restore(notification.getValue()); 
                            }
                        } else {
                            System.out.println("Just removed for some reason");
                        }
                    }
                }
        )
        .build(
                new CacheLoader<String, Integer>() {
                    public Integer load(String key) throws Exception {
                        return new Integer(-1);
                    }
                });

回答1:

Try Static class with isExternalCondition() method.

来源：https://stackoverflow.com/questions/21990133/guava-cachebuilder-imply-additional-conditions-to-entity-removal