可以通过将类括在方括号内来表明这是一个类；在括号中，可以有一组字符或者用破折号指定的字符范围。
You can indicate a class by surrounding it in square braces; within the braces, you can have both a set of characters and character ranges indicated with a dash.
注意方括号(不是圆括号)中需要组成一个匿名列表引用。
Note the brackets (not parentheses), which are required to compose an anonymous list reference.
注意：尖括号中的参数为可选参数；方括号()中的参数或选项为必需参数，必须提供。
Note: parameters shown in Angle brackets are optional; parameters or options shown in normal brackets () are required and must be provided.
以上在方括号中显示的语法部分可以省去(在此情况下，必须将括号也省去)。
Parts of the above syntax shown in square brackets can be left out (in which case you have to leave the brackets out too).
清单12还说明了DB 2中(方括号)和Oracle中(括号)中子索引的不同语法。
Listing 12 also illustrates the different syntax for sub-indexing in DB2 (square brackets) and in Oracle (parentheses).
在规则表达式中，方括号只表示“查找与方括号中任何字符的匹配字符”。
In regular expressions, square brackets just mean "match any character in the brackets."
在规则表达式中，方括号只表示“查找与方括号中任何字符的匹配字符”。
In regular expressions, square brackets just mean "match any character in the brackets."
应用推荐