java 使用正则表达式查找所有包含 3 个字母的单词

Find all words with 3 letters with regex

提问by user1170330

I'm trying to find all words with 3 letters in a string.
So in this list

我试图在一个字符串中找到所有包含 3 个字母的单词。
所以在这个列表中

cat monkey dog mouse

I only want

我只想要

cat dog

This is my expression:

这是我的表达：

^[a-zA-Z]{3}$

I tested it with different online regex tester, but none of them matched my expression.

我用不同的在线正则表达式测试器对其进行了测试，但没有一个与我的表达式匹配。

回答by anubhava

You should use your match with word boundaries instead of anchors:

您应该将匹配与单词边界而不是锚点一起使用：

\b[a-zA-Z]{3}\b

RegEx Demo

正则表达式演示

When you use:

当您使用：

^[a-zA-Z]{3}$

It means you want to match a line with exact 3 letters.

这意味着您要匹配具有精确 3 个字母的行。

回答by maioman

you can use .instead of [a-zA-Z]if you want to match any character (also numbers):

如果您想匹配任何字符（也包括数字），您可以使用.代替[a-zA-Z]：

 \b.{3}\b

回答by Ameya Pandilwar

1. To match all words with 3 letters in a string, the pattern needs to be "\b[a-zA-Z]{3}\b"

2. The next step would be to compile your pattern.

   Pattern pattern = Pattern.compile("\b[a-zA-Z]{3}\b");
   

3. Use a matcher and use the find() and group() methods to print the occurrences

   for (String word : sentence) {
       Matcher matcher = pattern.matcher(word);
       while(matcher.find()) {
           System.out.println(matcher.group());
       }
   }
   

4. Your program should look something like -

   public static void main(String[] args) {
       List<String> sentence = new ArrayList<String>();
       sentence.add("cat");
       sentence.add("monkey");
       sentence.add("dog");
       sentence.add("mouse");
   
       Pattern pattern = Pattern.compile("\b[a-zA-Z]{3}\b");
   
       for (String word : sentence) {
           Matcher matcher = pattern.matcher(word);
           while(matcher.find()) {
               System.out.println(matcher.group());
           }
       }
   }
   

1. 要匹配字符串中包含 3 个字母的所有单词，模式需要为"\b[a-zA-Z]{3}\b"

2. 下一步是编译您的模式。

   Pattern pattern = Pattern.compile("\b[a-zA-Z]{3}\b");
   

3. 使用匹配器并使用 find() 和 group() 方法打印出现的次数

   for (String word : sentence) {
       Matcher matcher = pattern.matcher(word);
       while(matcher.find()) {
           System.out.println(matcher.group());
       }
   }
   

4. 你的程序应该看起来像 -

   public static void main(String[] args) {
       List<String> sentence = new ArrayList<String>();
       sentence.add("cat");
       sentence.add("monkey");
       sentence.add("dog");
       sentence.add("mouse");
   
       Pattern pattern = Pattern.compile("\b[a-zA-Z]{3}\b");
   
       for (String word : sentence) {
           Matcher matcher = pattern.matcher(word);
           while(matcher.find()) {
               System.out.println(matcher.group());
           }
       }
   }