The extra variable is to avoid duplication and turns out to pay off in another way in the next step.

这个额外变量用于避免副本，事实证明，它将在下一步中以另一种方式带来好处。

youdao

Add an extra variable and two methods to the root bean in your data source, as Listing 8 shows. You can see these changes in the Root.java

在您的数据源中添加一个额外的变量和两中方法到您的根 bean 中，如 列表 8 所示。

youdao

Hence, the compiler cannot cache the value of a global variable in a register, resulting in extra (often unnecessary) loads and stores when globals are used.

所以编译器不会将全局变量存储在寄存器中，那样会带来额外的、不必要的负担和存储空间。

youdao

There's this weird extra variable in there called self.

好，这是关于面向对象编程,我们需要谈论一点的东西。

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