Question

I have a string in what is the best way to put the things in between $ inside a list in java?

String temp = $abc$and$xyz$;

how can i get all the variables within $ sign as a list in java
[abc, xyz]

i can do using stringtokenizer but want to avoid using it if possible.
thx

Answer 1

The pattern is simple enough that String.split should work here, but in the more general case, one alternative for StringTokenizer is the much more powerful java.util.Scanner.

    String text = "$abc$and$xyz$";
    Scanner sc = new Scanner(text);

    while (sc.findInLine("\\$([^$]*)\\$") != null) {
        System.out.println(sc.match().group(1));
    } // abc, xyz

The pattern to find is:

\$([^$]*)\$
  \_____/     i.e. literal $, a sequence of anything but $ (captured in group 1)
     1                 and another literal $

The […] is a character class. Something like [aeiou] matches one of any of the lowercase vowels. [^…] is a negated character class. [^aeiou] matches one of anything but the lowercase vowels.

(…) is used for grouping. (pattern) is a capturing group and creates a backreference.

The backslash preceding the $ (outside of character class definition) is used to escape the $, which has a special meaning as the end of line anchor. That backslash is doubled in a String literal: "\\" is a String of length one containing a backslash).

This is not a typical usage of Scanner (usually the delimiter pattern is set, and tokens are extracted using next), but it does show how’d you use findInLine to find an arbitrary pattern (ignoring delimiters), and then using match() to access the MatchResult, from which you can get individual group captures.

You can also use this Pattern in a Matcher find() loop directly.

    Matcher m = Pattern.compile("\\$([^$]*)\\$").matcher(text);
    while (m.find()) {
        System.out.println(m.group(1));
    } // abc, xyz

Related questions

• Validating input using java.util.Scanner
• Scanner vs. StringTokenizer vs. String.Split