The best way to find out that part of the string is potencial RegEx match

how would you do this:

I have a string and some regexes. Then I iterate开发者_JAVA技巧 over the string and in every iteration I need to know if the part (string index 0 to string currently iterated index) of that string is possible full match of one or more given regexes in next iterations.

Thank you for help.

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What about a code like this:

// all of *greedy* regexs into a list
List<String> regex = new ArrayList<String>();
// here is my text
String mytext = "...";

String tmp = null;
// iterate over letters of my text
for (int i = 0; i < mytext.length(); i++) {
     // substring from 0. position till i. index
     tmp = mytext.substring(0, i);
     // append regex on sub text
     for (String reg : regex ) {
          Pattern p = Pattern.compile(reg);
          Matcher m = p.matcher(tmp);
          // if found, do smt
          if (m.find() ) { bingo.. do smt! }
     }     
}

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You could use Matcher.lookingAt() to try to match as much as possible from a given input, but not requiring the whole input to match (.matches() would require the full input to match and .find() would not require the match to start at the beginning).

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I don't believe the Java regular expression API provides such "incremental" or "step-by-step" search.

What you could do however, is to formulate your expression using reluctant quantifiers.

[...] The reluctant quantifiers, however, take the opposite approach: They start at the beginning of the input string, then reluctantly eat one character at a time looking for a match. The last thing they try is the entire input string. [...]

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If this isn't viable in your case, you could use the Matcher.setRegion method to incrementally increase the region used by the matcher.

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So I've been searching for alternatives to Java's standart RegEx library and found one that does the job well - JRegex