java - 正则表达式: Match pattern `foo` but not incase if it occurs after pattern `bar`

Question

匹配模式foo但如果它出现在模式 bar 之后则不然。基本上给定一个字符串，我“尝试”匹配开始标签 <任何字符串 >如果匹配位于结束标记 </ 之后，则不应发生匹配任何字符串 > 。

注意:我正在“尝试”类似的方法来解决，这可能不是解决方案的实际路径。如果您能帮助解决当前问题，我将非常高兴。

所以它应该匹配:
<h1>在<h1>
<h1>在<h1> abc </h1>
<abc>在<abc>something</cde><efg>
<abc>在something<abc>something

不应匹配以下内容:
</h1>
</abc> one two three <abc> five six <abc>
one two three </abc> five six <abc>

Answer 1

最简单的解决方案是将部分工作外包给 java regex API。使用正则表达式，我们只能匹配 <[^>]*> ，即任何 html 标签。然后我们可以使用Matcher.region()将匹配限制为任何 </ 之前的字符串.

这是代码:

    // example data
    String[] inputLines = {
            "<h1>",
            "<h1> abc </h1>",
            "<abc>something</cde><efg>",
            "something<abc>something",
            "",
            "</h1>",
            "</abc> one two three <abc> five six <abc>",
            "one two three </abc> five six <abc>"
    };

    // the pattern for any html tag
    Pattern pattern = Pattern.compile("<[^>]*>");

    for (String line : inputLines) {
        Matcher matcher = pattern.matcher(line);
        // the index that we must not search after
        int undesiredStart = line.indexOf("</");

        //  undesiredStart == -1 ? line.length() : undesiredStart handles the undesired not found case. In that case the region end must be the length of the string
        matcher.region(0, undesiredStart == -1 ? line.length() : undesiredStart);

        // this is the idiom to iterate through the matches
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }