IDEA is a symmetricmethod to crypt message or document.
设想是对称的方法隐窝邮件或文件。
2
We can well imagine the need to reactivate a deactivated cell phone, and so we should decide whether we should also offer the symmetric activate method.
我们完全可以想象会需要对弃用的手机进行重新激活，因此应决定是否也应提供对称的Activate方法。
3
If you try to override the Object.equals method in OrderFulfillment such that it is "equal" to its Order, you've broken the contract of Object.equals, which specifies that equality must be symmetric.