找不到符號java.awt和java.util

Question

我正在使用NB.the ide給出的錯誤是它找不到符號java.awt。嘗試在eclipse.it中運行相同的代碼也會產生相同的錯誤。它甚至在創建新的JFrame時都會給出錯誤找不到符號。

錯誤：

Answer 1

名爲java類掩蓋了包名java，看到Java Language Specification 6.4.2：

A simple name may occur in contexts where it may potentially be interpreted as the name of a variable, a type, or a package. In these situations, the rules of §6.5 specify that a variable will be chosen in preference to a type, and that a type will be chosen in preference to a package. Thus, it is may sometimes be impossible to refer to a visible type or package declaration via its simple name. We say that such a declaration is obscured.

這意味着，包含類的包內0​​你不會能夠通過限定名稱引用任何java.*包中的類。

但是你仍然可以導入你需要的類，並通過簡單名稱引用它們：

import java.util.logging.Logger; 
import java.awt.EventQueue; 

// within some method: 
    Logger.getLogger(....);