如何只使用java正则表达式匹配字母，匹配方法？ [英] How to match letters only using java regex, matches method?

问题描述

import java.util.regex.Pattern;

class HowEasy {
    public boolean matches(String regex) {
        System.out.println(Pattern.matches(regex, "abcABC   "));
        return Pattern.matches(regex, "abcABC");
    }

    public static void main(String[] args) {
        HowEasy words = new HowEasy();
        words.matches("[a-zA-Z]");
    }
}

输出为False。我哪里错了？此外，我想检查一个单词是否只包含字母，并且可能或可能不以一个句点结束。那是什么样的正则表达式？

The output is False. Where am I going wrong? Also I want to check if a word contains only letters and may or maynot end with a single period. What is the regex for that?

即abcabc。有效但abc ..无效。

i.e "abc" "abc." is valid but "abc.." is not valid.

我可以用 indexOf（）方法解决它，但我想知道是否可以使用一个正则表达式。

I can use indexOf() method to solve it, but I want to know if it is possible to use a single regex.

推荐答案

[a-zA-Z]只匹配一个字符。要匹配多个字符，请使用[a-zA-Z] +。

"[a-zA-Z]" matches only one character. To match multiple characters, use "[a-zA-Z]+".

由于点是a任何角色的小丑，你必须掩饰它：abc \。要使点可选，你需要一个问号：
abc \。？

Since a dot is a joker for any character, you have to mask it: "abc\." To make the dot optional, you need a question mark: "abc\.?"

如果在代码中将Pattern写为文字常量，则必须屏蔽反斜杠：

If you write the Pattern as literal constant in your code, you have to mask the backslash:

System.out.println ("abc".matches ("abc\\.?"));
System.out.println ("abc.".matches ("abc\\.?"));
System.out.println ("abc..".matches ("abc\\.?"));

结合两种模式：

System.out.println ("abc.".matches ("[a-zA-Z]+\\.?"));

而不是a-zA-Z，\ w通常更合适，因为它捕获外来字符喜欢äöüßø等等：

Instead of a-zA-Z, \w is often more appropriate, since it captures foreign characters like äöüßø and so on:

System.out.println ("abc.".matches ("\\w+\\.?"));   

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