如何在两个字符串之间找到值？

Question

How would I "find" and "get" a value between two strings?

ie: <a>3</a>

I'm reading a file to find the location of <a> , where that starts, then it will stop reading when it finds </a> The value I want to return is "3".

Using JRE 6

Answer 1

Your two main options are:

1) preferred but potentially complicated : using an XML/HTML parser and getting the text within the first "a" element. eg using Jsoup (thanks @alpha123):

Jsoup.parse("<a>3</a>").select("a").first().text(); // => "3"

2) easier but not very reliable : using a regular expression to extract the characters between the <a> and </a> strings. eg:

String s = "<a>3</a>";
Pattern p = Pattern.compile("<a>(.*?)</a>")
Matcher m = p.matcher(s);
if (m.find()) {
  System.out.println(m.group(1)); // => "3"
}

Answer 2

Jsoup将很容易做到这一点。

String title = Jsoup.parse("<a>3</a>").select("a").first().text();

Answer 3

You can use regex:

try {
    Pattern regex = Pattern.compile("<a>(.*)</a>");
    Matcher regexMatcher = regex.matcher(subjectString);
    while (regexMatcher.find()) {
        for (int i = 1; i <= regexMatcher.groupCount(); i++) {
            // matched text: regexMatcher.group(i)
            // match start: regexMatcher.start(i)
            // match end: regexMatcher.end(i)
        }
    } 
} catch (PatternSyntaxException ex) {
    // Syntax error in the regular expression
}

But, if your input is HTML, you should really consider using an HTML parser.