substring between two delimiters

问题:

I have a string as : "This is a URL http://www.google.com/MyDoc.pdf which should be used"

I just need to extract the URL that is starting from http and ending at pdf : http://www.google.com/MyDoc.pdf

String sLeftDelimiter = "http://";
String[] tempURL = sValueFromAddAtt.split(sLeftDelimiter );
String sRequiredURL = sLeftDelimiter + tempURL[1];

This gives me the output as "http://www.google.com/MyDoc.pdf which should be used"

Need help on this.

回答1:

This kind of problem is what regular expressions were made for:

Pattern findUrl = Pattern.compile("\\bhttp.*?\\.pdf\\b");
Matcher matcher = findUrl.matcher("This is a URL http://www.google.com/MyDoc.pdf which should be used");
while (matcher.find()) {
  System.out.println(matcher.group());
}

The regular expression explained:

• \b before the "http" there is a word boundary (i.e. xhttp does not match)
• http the string "http" (be aware that this also matches "https" and "httpsomething")
• .*? any character (.) any number of times (*), but try to use the least amount of characters (?)
• \.pdf the literal string ".pdf"
• \b after the ".pdf" there is a word boundary (i.e. .pdfoo does not match)

If you would like to match only http and https, try to use this instead of http in your string:

• https?\: - this matches the string http, then an optional "s" (indicated by the ? after the s) and then a colon.

回答2:

why don't you use startsWith("http://") and endsWith(".pdf") mthods of String class.

Both the method returns boolean value, if both returns true, then your condition succeed else your condition is failed.

回答3:

Try this

String StringName="This is a URL http://www.google.com/MyDoc.pdf which should be used";

StringName=StringName.substring(StringName.indexOf("http:"),StringName.indexOf("which"));

回答4:

You can use Regular Expression power for here. First you have to find Url in original string then remove other part.

Following code shows my suggestion:

    String regex = "\\b(http|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]";
    String str = "This is a URL http://www.google.com/MyDoc.pdf which should be used";

    String[] splited = str.split(regex);

    for(String current_part : splited)
    {
        str = str.replace(current_part, "");
    }

    System.out.println(str);

This snippet code cans retrieve any url in any string with any pattern. You cant add customize protocol such as https to protocol part in above regular expression.

I hope my answer help you ;)

回答5:

public static String getStringBetweenStrings(String aString, String aPattern1, String aPattern2) {
    String ret = null;
    int pos1,pos2;

    pos1 = aString.indexOf(aPattern1) + aPattern1.length();
    pos2 = aString.indexOf(aPattern2);

    if ((pos1>0) && (pos2>0) && (pos2 > pos1)) {
        return aString.substring(pos1, pos2);
    }

    return ret;
}

回答6:

You can use String.replaceAll with a capturing group and back reference for a very concise solution:

String input = "This is a URL http://www.google.com/MyDoc.pdf which should be used";
System.out.println(input.replaceAll(".*(http.*?\\.pdf).*", "$1"));

Here's a breakdown for the regex: https://regexr.com/3qmus