Java parsing and extract String from pattern String

Question

I want to extract some string surrounded by certain patterns.

For Instance, the original String something like 1234@{78}dasdh@{1}fdsfs@{fdf}ad@{ and I want extract 78, 1, fdf from it.

Below is my code for the purpose

public class Test { // want to get "78", "1", "fdf" private static String targetStr = "1234@{78}dasdh@{1}fdsfs@{fdf}ad@{"; public static void main (String[] args) throws Exception { List<String> parsed = new ArrayList<>(); Pattern open = Pattern.compile("@\\{"); Matcher oMatcher = open.matcher(targetStr); Pattern close = Pattern.compile("}"); Matcher cMatcher = close.matcher(targetStr); while(oMatcher.find()) { if(cMatcher.find()) parsed.add(targetStr.substring(oMatcher.start() + 2, cMatcher.start())); } System.out.println(parsed); } } 

Is there anyway to complete this task? Some how it feels unsafe since use 2 iterator without any validation.

Answer 1

There's a simpler way:

Pattern p = Pattern.compile("\\w+@\\{(\\w+)\\}"); Matcher m = p.matcher(targetStr); while (m.find()) { parsed.add(m.group(1)); } 

Instead of matching the opening and closing braces separately, the above pattern matches a whole expression of the form aaa@{bbb} at once. And when it finds the expression, it remembers the part inside the braces. This is done via a capturing group (the parentheses).

To learn more about each of the characters in the pattern, read the Javadoc of the Pattern class.