java8函數表達式的定義［Definition of a Lambda Expression］

英文來源於：Java in a Nutshell, 6th Edition

　　　　　　　　　　　Definition of a Lambda Expression A lambda expression is essentially a function that does not have a name, and can be treated as a value in the language. As Java does not allow code to run around on its own outside of classes, in Java, this means that a lambda is an anonymous method that is defined on some class (that is possibly unknown to the developer). 　　　　　　　　　　　　　　　　　　　　　　　　---Java in a Nutshell, 6th Edition

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其實正則表達式就是沒有名字的函數，（參數，返回值，函數體），在java　語言中視爲一個值． 由於java的函數必須在類中定義，這就意味着，java語言中的函數表達式即爲在某類中定義的匿名方法．

函數表達式在java視爲一個值，即：Runnable r = () -> System.out.println("Hello World");　形式．