对于那些只使用1到2个正则表达式的小型的应用程序，这意味着没有必要每次都创建一个Regex对象。

For those little utility applications that only use one or two expressions, this means explicitly creating a RegEx object is probably not necessary.

youdao

XPathExpression对象通过将XPath表达式的String表示传递给XPath的编译方法来创建。

XPathExpression objects are created by passing a String representation of the XPath expression into the compile method on XPath.

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创建工厂之后，还需要从工厂转移到能够真正计算表达式并与XPath环境交互的对象。

Once you've created your factory, you need to move from it to an object that can actually evaluate expressions and interact with the XPath environment.

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