java split()的用法注意

Splits this string around matches of the given regular expression .

The array returned by this method contains each substring of this string that is terminated by another substring that matches the given expression or is terminated by the end of the string. The substrings in the array are in the order in which they occur in this string. If the expression does not match any part of the input then the resulting array has just one element, namely this string.

The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array. If the limit n is greater than zero then the pattern will be applied at most n  - 1 times , the array's length will be no greater than n , and the array's last entry will contain all input beyond the last matched delimiter. If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

The string "boo:and:foo" , for example, yields the following results with these parameters:

Regex Limit Result

:	2	{ "boo", "and:foo" }
:	5	{ "boo", "and", "foo" }
:	-2	{ "boo", "and", "foo" }
o	5	{ "b", "", ":and:f", "", "" }
o	-2	{ "b", "", ":and:f", "", "" }
o	0	{ "b", "", ":and:f" }

An invocation of this method of the form str. split( regex ,  n ) yields the same result as the expression

java.util.regex.Pattern .compile ( regex ) .split ( str ,  n )

Parameters:

regex the delimiting regular expression

limit the result threshold, as described above

Returns:

the array of strings computed by splitting this string around matches of the given regular expression

 

以上是jdk的官方文档，

默认的split(regex)方法会以split(regex,0)调用

 

当limit N 大于0时，会匹配N-1次，数组长度最大为N，返回数组的最后一个元素会把数组最后的所有字符包括进来

 

当limit N 小于0时，会匹配尽可能多次，返回最大长度的数组

 

当limit N 等于0时，会匹配尽可能多次，返回最大长度的数组，并且末尾的空串不会包含进来