* 和 + 正则表达式的区别 [英] Difference between * and + regex

问题描述

谁能告诉我下面示例中 * 和 + 运算符之间的区别:

Can anybody tell me the difference between the * and + operators in the example below:

[<>]+ [<>]*

推荐答案

每个都是量词，星形量词(*) 表示前面的表达式可以匹配零次或多次，就像{0,} 而加号(+)表示前面的表达式必须至少匹配一次或多次并且与{1相同,} .

Each of them are quantifiers, the star quantifier(*) means that the preceding expression can match zero or more times it is like {0,} while the plus quantifier(+) indicate that the preceding expression MUST match at least one time or multiple times and it is the same as {1,} .

总结一下:

a*  ---> a{0,}  ---> Match a or aa or aaaaa or an empty string
a+  ---> a{1,}  ---> Match a or aa or aaaa but not a string empty

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