Java文法(2)—— 语句分析文法

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扩展一(换行符定义):
	LineTerminator:
		the ASCII LF character, also known as "newline"
		the ASCII CR character, also known as "return"
		the ASCII CR character followed by the ASCII LF character
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扩展二(换行符过滤语法):
	InputCharacter:
		UnicodeInputCharacter but not CR or LF
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扩展三(句子文法定义):
	Input:
		InputElements opt Sub opt
	InputElements:
		InputElement
		InputElements InputElement
	InputElement:
		WhiteSpace
		Comment
		Token
		Token:
		Identifier
		Keyword
		Literal
		Separator
		Operator
	Sub:
		the ASCII SUB character, also known as "control-Z"
	说明:
		过滤换行符后的句子文法定义
		The input characters and line terminators that result from escape processing (§3.3)
		and then input line recognition (§3.4) are reduced to a sequence of input elements.
		Those input elements that are not white space (§3.6) or comments (§3.7) are tokens.
		The tokens are the terminal symbols of the syntactic grammar (§2.3).
		White space (§3.6) and comments (§3.7) can serve to separate tokens that, if
		adjacent, might be tokenized in another manner. For example, the ASCII characters
		- and = in the input can form the operator token -= (§3.12) only if there is no
		intervening white space or comment.
		As a special concession for compatibility with certain operating systems, the ASCII
		SUB character ( \u001a , or control-Z) is ignored if it is the last character in the
		escaped input stream.
		Consider two tokens x and y in the resulting input stream. If x precedes y , then we
		say that x is to the left of y and that y is to the right of x .
		For example, in this simple piece of code:
		class Empty {
		}
		we say that the } token is to the right of the { token, even though it appears, in this two-
		dimensional representation, downward and to the left of the { token. This convention about
		the use of the words left and right allows us to speak, for example, of the right-hand operand
		of a binary operator or of the left-hand side of an assignment.