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.

• Timothy Truckle: I'm voting to close this question as off-topic because it could be solved by looking at the public online documentation.
• t3chb0t: Is there anyway to complete this task? You mean any better way to complete this task, right? Or isn't this code working yet?
• Juneyoung Oh: @t3chb0t yes. I mistook about the words. Thanks
• Juneyoung Oh: @TimothyTruckle It is ok to close, but I would like to know which is the best way to implement that function. In my thought working code and optimized code is different.
• Timothy Truckle: @JuneyoungOh: "but I would like to know which is the best way to implement that function." As the answer of Roland Illig shows there is a better way and you could have found it your self by reading the free online documentation as I mentioned.

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.

• Juneyoung Oh: Thanks! I did not know about group methods.
• t3chb0t: There's a simpler way: - could you add a short description which way and/or why for poeple - like me ;-) who are unable to find the difference?
• Roland Illig: @t3chb0t Thanks for the suggestion. It reads much better now.