Regex and escaped and unescaped delimiter

Question

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I have a string

a\\;b\\\\;c;d

which in Java looks like

String s = \"a\\\\;b\\\\\\\\;c;d\"         


        

Answer 1

I do not trust to detect those cases with any kind of regular expression. I usually do a simple loop for such things, I'll sketch it using C since it's ages ago I last touched Java ;-)

int i, len, state;
char c;

for (len=myString.size(), state=0, i=0; i < len; i++) {
    c=myString[i];
    if (state == 0) {
       if (c == '\\') {
            state++;
       } else if (c == ';') {
           printf("; at offset %d", i);
       }
    } else {
        state--;
    }
}

The advantages are:

1. you can execute semantic actions on each step.
2. it's quite easy to port it to another language.
3. you don't need to include the complete regex library just for this simple task, which adds to portability.
4. it should be a lot faster than the regular expression matcher.