在字符串中搜索单词 [英] Search for a word in a String
问题描述
如果我在字符串中查找特定单词，例如，在字符串你好吗我正在寻找是。
常规indexOf（）工作得更快更好还是正则表达式匹配（）
字符串testStr =怎么样您;
String lookUp =are;
// METHOD1
if（testStr.indexOf（lookUp）！= -1）
{
System.out.println（Found！）;
}
// OR
//方法2
if（testStr.match（。*+ lookUp +。*））
{
System.out.println（Found！）;
}
上述两种方法中的哪一种是查找内部字符串的更好方法另一串？或者有更好的选择吗？
- Ivard
如果你不关心它是否真的是你匹配的整个单词，那么 indexOf（）将是更快。
另一方面，如果你需要能够区分 ， harebrained ，不是等等，那么你需要一个正则表达式： \ bare \ b 只会将 作为整个单词匹配（ \\bare\\b b
$ b
\ b 是一个单词边界锚点，它与空白空间匹配在字母数字字符（字母，数字或下划线）和非字母数字字符之间。
警告：这也意味着，如果您的搜索字词实际上不是一个字（假设您正在寻找 ### ），然后这些单词边界锚点只匹配 aaa ### zzz 之类的字符串，但不会出现在 +++中### +++ 。
进一步警告：默认情况下，Java对于构成字母数字字符的内容有一个有限的世界观。此处只有ASCII字母/数字（加上下划线）计数，因此单词边界锚点会在élève，relevé或ärgern。 了解更多相关信息（以及如何解决此问题）这里。
If I am looking for a particular word inside a string, for example, in the string "how are you" I am looking for "are". Would a regular indexOf() work faster and better or a Regex match()
String testStr = "how are you";
String lookUp = "are";
//METHOD1
if (testStr.indexOf(lookUp) != -1)
{
System.out.println("Found!");
}
//OR
//METHOD 2
if (testStr.match(".*"+lookUp+".*"))
{
System.out.println("Found!");
}
Which of the two methods above is a better way of looking for a string inside another string? Or is there a much better alternative?
- Ivard
If you don't care whether it's actually the entire word you're matching, then indexOf() will be a lot faster.
If, on the other hand, you need to be able to differentiate between are, harebrained, aren't etc., then you need a regex: \bare\b will only match are as an entire word (\\bare\\b in Java).
\b is a word boundary anchor, and it matches the empty space between an alphanumeric character (letter, digit, or underscore) and a non-alphanumeric character.
Caveat: This also means that if your search term isn't actually a word (let's say you're looking for ###), then these word boundary anchors will only match in a string like aaa###zzz, but not in +++###+++.
Further caveat: Java has by default a limited worldview on what constitutes an alphanumeric character. Only ASCII letters/digits (plus the underscore) count here, so word boundary anchors will fail on words like élève, relevé or ärgern. Read more about this (and how to solve this problem) here.
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