If a page action method invocation returns a non-null string value, Seam treats it as a navigation event.

如果页面动作方法调用返回一个非空字符串值，则Seam将其当作一个导航事件。

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You might wonder about the String class given the issue of out-of-order writes and a reference becoming non-null prior to the constructor executing. Consider the following code.

鉴于无序写入和引用在构造函数执行前变成非null的问题，您可能会考虑string类。

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