A good, hygienic way of doing this is, not only do I not go in and change things except through a pre-defined method, I shouldn't read it other Cartesian than through a pre-defined method.

做这个的方式是，我不仅仅要通过提前定义好的方法,来改变数值,我还应该通过提前定义好的方法，来读这个值,我应该用。

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