副作用 - 这是什么？ [英] Side effect--what's this?

问题描述

有人可以在下一行告诉我副作用的含义吗？

Could someone tell me the meaning of "side effect" in the following line?

如果你正在调用一个EL函数没有返回任何东西，那么你只是因为它的副作用而调用它。

If you're calling an EL function that doesn't return anything, then you're calling it just for its side effects.

推荐答案

副作用是除了计算和返回值之外的任何方法。实例或类字段值的任何更改都是副作用，就像在屏幕上绘制内容，写入文件或网络连接一样。

A side effect is anything a method does besides computing and returning a value. Any change of instance or class field values is a side effect, as is drawing something on the screen, writing to a file or a network connection.

严格来说，函数被定义为没有副作用 - 这就是Java使用方法一词的原因。没有返回值的真正函数将毫无意义。

Strictly speaking, a "function" is defined as not having side effects - which is why Java uses the word "method" instead. A real function with no return value would be pointless.

显然，没有返回值的方法必须具有某种副作用，证明其存在是正确的。设置方法就是一个例子 - 副作用是改变对象的内部状态。

Obviously, a method that does not have a return value must have some sort of side effect that justifies its existence. Set methods are an example - the side effect is changing the object's internal state.

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