Question

我有一个文本文档，其中有一堆/courses/......./.../..形式的网址从这些网址中，我只想提取/courses/.../lecture-notes形式的网址。表示以/courses开头并以/lecture-notes结尾的网址。有没有人知道用正则表达式或仅通过字符串匹配来做这个的好方法？

Answer 1

这是另一种选择：

Scanner s = new Scanner(new FileReader("filename.txt"));

String str;
while (null != (str = s.findWithinHorizon("/courses/\\S*/lecture-notes", 0)))
    System.out.println(str);

给定filename.txt内容

Here /courses/lorem/lecture-notes and
here /courses/ipsum/dolor/lecture-notes perhaps.

以上代码段打印

/courses/lorem/lecture-notes
/courses/ipsum/dolor/lecture-notes

Answer 2

假设每行有1个URL，可以使用：

    BufferedReader br = new BufferedReader(new FileReader("urls.txt"));
    String urlLine;
    while ((urlLine = br.readLine()) != null) {
        if (urlLine.matches("/courses/.*/lecture-notes")) {
            // use url
        }
    }

Answer 3

以下将仅返回中间部分（即：排除/courses/和/lectures-notes/：

Pattern p = Pattern.compile("/courses/(.*)/lectures-notes");
Matcher m = p.matcher(yourStrnig);

if(m.find()).
  return m.group(1) // The "1" here means it'll return the first part of the regex between parethesis.

使用java从文本文件中提取特定URL

3 个答案: