java - 我的正则表达式有什么问题 -?\\d{2}\\.?\\d{6}

Question

我正在尝试从 url 中提取纬度和经度:

source:...sensor=false¢er=-15.842208999999999%2C-48.023084&zoom=17&size=256x256&language=en&client=google-maps-frontend&signature=hbey3U4lycTNgX48asW8MODjJLM

I'm not good in regexes, so I used this regex tester (http://regexpal.com/) and coded this regex

-?\d{2}\.?\d{6}

(is for JAVA )

It produces this result (who's saying it is regexpal.com):

-15.842208 ... -48.023084

So when I do it (in java):

for (Element element : newsHeadlines) {
        if(element.toString().contains("https://maps.google.com")){
            List<String> lista = get_matches(element.attr("content"), "-?\\d{2}\\.?\\d{6}");


        }
    }

public static List<String> get_matches(String s, String p) {
    // returns all matches of p in s for first group in regular expression 
    List<String> matches = new ArrayList<String>();
    Matcher m = Pattern.compile(p).matcher(s);
    while(m.find()) { 
        matches.add(m.group(1)); //<-- Exception m.group(1) not have any results.
    }
    return matches;
}

我的正则表达式有什么问题？

Answer 1

您的方法 get_matches 正在寻找 m.group(1) 组在带括号的正则表达式中定义。所以你的正则表达式需要像这样:

(-?\\d{2}\\.?\\d{6})

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