java - 不确定在这种情况下字符串拆分实际上是如何工作的

Question

我没有得到以下内容:

在以下字符串中:

String s = "1234;x;;y;";

如果我这样做:
String[] s2 = s.split(";");

我得到 s2.length 为 4 和

s2[0] = "1234";  
s2[1] = "x";  
s2[2] = "";  
s2[3] = "y"; 

但在字符串中:String s = "1234;x;y;;";

我得到:

s2.length 为 3 和

s2[0] = "1234";  
s2[1] = "x";  
s2[2] = "y"; 

?

有什么区别，在后一种情况下我也没有得到 4？

更新:
使用 -1 并不是我所期望的行为。
我的意思是最后一个分号是 String 的结尾，所以在后一个示例中我还期望 4 作为数组的长度

Answer 1

来自docs ,

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

更新:

您有五个由 分隔的子字符串； 在第二种情况下，它们是 1234、x、y 、 和 。根据文档，拆分操作产生的所有空子字符串(末尾)都将被消除。详情看here .

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.

例如，字符串 boo:and:foo 使用这些参数产生以下结果:

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" }   // all the empty substrings at the end were eliminated