Before we can do anything String-specific with that retrieved value, we have to cast it to a String, even when the retrieved element was added in the same code block!
在对检索到的值进行任何特定于String的操作之前，必须将它强制转换为String，即使是将检索到的元素添加到同一代码块中，也是如此！
To specify an int variable for an iterator and a String variable for element name, use the code in Listing 17.
要为迭代器指定一个int变量并为元素名称指定一个String变量，请使用清单17中的代码。
The call to filter converts the string that is passed as its second argument to a piece of code, which it then applies to each element of the list that is passed as its first argument.
调用filter将作为第二个参数传递的字符串转换成一段代码，然后将该代码应用到作为第一个参数传递的列表的每个元素。
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