Java中的正则表达式是否默认使用^和$字符锚定？ [英] Is regex in Java anchored by default with both a ^ and $ character?

问题描述

根据我对正则表达式的理解，字符串00 ###必须与[0-9]匹配，但不能与^ [0-9] $匹配。但它不适用于Java regexp。

From my understanding of regular expressions, the string "00###" has to match with "[0-9]", but not with "^[0-9]$". But it doesn't work with Java regexp's.

在对此问题进行一些调查后，我发现了以下信息（ http://www.wellho.net/solutions/java-regular-expressions-in-java.html ）：

After some investigating of this problem I found the following information (http://www.wellho.net/solutions/java-regular-expressions-in-java.html):

看起来Java常规
表达式默认用
锚定^和$字符。

It might appear that Java regular expressions are default anchored with both a ^ and $ character.

我们可以确定所有版本的JDK都适用吗？并且可以关闭此模式（即禁用^和$的默认锚定）？

Can we be sure that this is true for all versions of JDK? And can this mode be turned off (i.e. to disable default anchoring with ^ and $)?

推荐答案

正如您所链接的文章所解释的那样，它取决于您调用的功能。如果要在默认情况下添加^和$，请使用 String＃matches 或 匹配＃匹配 。如果您不想这样，请使用 匹配#find 方法。

As the article you linked to explains, it depends on the function you call. If you want to add ^ and $ by default, use String#matches or Matcher#matches. If you don't want that, use the Matcher#find method instead.

import java.util.regex.*;

public class Example
{
    public static void main(String[] args)
    {
        System.out.println("Matches: " + "abc".matches("a+"));

        Matcher matcher = Pattern.compile("a+").matcher("abc");
        System.out.println("Find: " + matcher.find());
    }
}

输出：

Matches: false
Find: true

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