有时，使用简单的基于时间的对象过期更为容易和简洁。
Sometimes, it's easier and cleaner to use simple timed-based expiration of objects.
执行HTTP缓存时，最重要的部分就是确定哪些对象可以存储在缓存之中，以及这些对象将在何时过期等。
The most important part of performing HTTP caching is determining which objects can be stored in the cache, when they are to expire, etc.
这个技术允许缓存Cells视图，直到一个加载的版本更新方法决定其已经过期，而不会使得一个Cell实例失去其面向对象的特性。
It allows Cell views to be cached until an attached versioning method decides to expire it, without loosing the object-oriented features of a Cell instance.
Dholakia的研究发现，有22%的被调查对象并没有使用Groupon优惠券，而是让它们过期作废，然而他提醒人们在这项指标上业主提供的数据有点水份。
Dholakia's study found that 22% of respondents allowed their Groupon coupons to expire without being used, though he warns that vendors' data was somewhat spotty on that metric.
超过30%的调查对象表示：他们任由食物过期或不吃而把钱浪费掉了，虽然很少有人愿意试着做出改变。
More than 30 percent said they wasted money by letting food expire or otherwise go uneaten, though few were willing to try to change that.
如果使用恰当，缓存可以极大地提升性能，譬如，将经常使用的数据缓存，按需要的时间设置过期。相信我，在老的asp技术中，将对象存入Session中有时会出现问题。
Caching can be great for increasing performance if used in the right way, i.e. you cache the data that will be accessed the most and you don't cache it for longer than you need.
同样，可能读到一个引用变量的最新值，但读取到这个引用变量引用的对象的字段的过期值。
Similarly, it is possible to read a fresh, updated value of a reference variable, but a stale value of one of the fields of the object now being referenced.
比如，得到一个对象的一个字段的最新值，同时得到这个对象的其他字段的过期的值。
For example, it is possible to obtain a fresh value for one field of an object, but a stale value for another.
比如，得到一个对象的一个字段的最新值，同时得到这个对象的其他字段的过期的值。
For example, it is possible to obtain a fresh value for one field of an object, but a stale value for another.
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