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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。我期待类似 no_of_characters + 1 的东西。有人可以解释一下，在这种情况下 split() 方法实际上做了什么？我只是不明白...

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1 回答 1

14

它拆分"\\S"正则表达式引擎中代表\S非空白字符的每个字符。

因此，让我们尝试"x x"在非空白 ( \S) 上进行拆分。由于这个正则表达式可以被一个字符匹配，让我们遍历它们以标记拆分位置（我们将使用管道|）。

  • 是非'x'空格吗？是的，所以让我们标记它| x
  • 是非' '空格吗？不，所以我们保持原样
  • 最后一个'x'非空格？是的，所以让我们标记它| |

因此，我们需要在开始和结束时拆分我们的字符串，这最初给了我们结果数组

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

但是由于删除了尾随的空字符串，结果将是

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

所以 split 返回["", " "]仅包含两个元素的数组。

顺便提一句。要关闭删除最后一个空字符串，您需要使用split(regex,limit)负值限制，例如split("\\S",-1).

现在让我们回到你的例子。对于您的数据，您将在每个数据上进行拆分

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

意思是

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

所以这代表这个数组

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

但是由于""删除了尾随的空字符串（如果它们的存在是由拆分引起的-更多信息请参见：来自 String.split 的混淆输出）

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

你得到的结果数组只包含这部分：

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

正好是 16 个元素。

于 2014-03-07T20:17:25.923 回答