Question

我正在准备OCPJP考试，我遇到了以下示例：

class Test {
   public static void main(String args[]) {
      String test = "I am preparing for OCPJP";
      String[] tokens = test.split("\\S");
      System.out.println(tokens.length);
   }
}

此代码打印16.我期待像no_of_characters + 1这样的东西。有人可以解释一下，split（）方法在这种情况下实际上做了什么？我只是不明白......

Answer 1

它在正则表达式引擎中表示"\\S"非空白字符的每个\S上分裂。

因此，我们尝试在非空格（"x x"）上拆分\S。由于这个正则表达式可以匹配一个字符，我们可以迭代它们以标记拆分位置（我们将使用管道|）。

是'x'非空白？是的，所以我们将其标记为| x
是' '非空白？不，所以我们保持原样
是最后'x'非空白？是的，所以我们将其标记为| |

因此，我们需要在开始和结束时拆分我们的字符串，最初给出结果数组

["", " ", ""]
   ^    ^ - here we split

但是由于删除了尾随空字符串，结果将是

[""," "]     <- result
        ,""] <- removed trailing empty string

所以split返回数组["", " "]，它只包含两个元素。

顺便说一句。要关闭删除最后一个空字符串，您需要使用split(regex,limit)，其值为负值split("\\S",-1)。

现在让我们回到你的例子。如果你的数据是分裂的

I am preparing for OCPJP
| || ||||||||| ||| |||||

表示

 ""|" "|""|" "|""|""|""|""|""|""|""|""|" "|""|""|" "|""|""|""|""|""

所以这代表了这个数组

[""," ",""," ","","","","","","","",""," ","",""," ","","","","",""]

但由于尾随空字符串""被删除（如果它们的存在是由分裂引起的 - 更多信息请参见：Confusing output from String.split）

[""," ",""," ","","","","","","","",""," ","",""," ","","","","",""]  
                                                     ^^ ^^ ^^ ^^ ^^

你得到的结果数组只包含这部分：

[""," ",""," ","","","","","","","",""," ","",""," "]

正好是16个元素。

当提供正则表达式时，Java中的String.split（）方法究竟是如何工作的？

1 个答案: