Java中的组和模式匹配

Question

How I can differentiate this string with Matcher and Pattern class?

I tried like this

String question="A: this is data i want first  B: this is data i want second  C: this is data i want  third A: this is data i want first  B: this is data i want second  C: this is data i want  third ";

Pattern pattern = Pattern.compile("A:(.*?)B:(.*?)C:(.*?)A:", Pattern.DOTALL | Pattern.MULTILINE);           
Matcher m = pattern.matcher(question);
while (m.find()) {
    m.group(1);
    m.group(2);
    m.group(3);
}

Answer 1

This is a bit of a hack but works if you don't find a better answer:

Use this regex:

A:(.*?)B:(.*?)C:(.*?)(?=A:)

But you'll have to append a delimiter to the string (your question variable):

Matcher m = pattern.matcher(question + "A:");

Used with println:

while (m.find()) {
    System.out.println(m.group(1));
    System.out.println(m.group(2));
    System.out.println(m.group(3));
}

It outputs:

this is data i want first
this is data i want second
this is data i want third
this is data i want first
this is data i want second
this is data i want third

Answer 2

As this requires a context, you could use a parser like ANTLR or you could code your own solution.

I would go with something like:

SplitterStringMatcher matcher = new SplitterStringMatcher {
    private char delimiter = 'A';
    // return the count of characters matched, 0 if none
    @Override public int matches(String str, int pos) {
        if (str.length() > pos + 1
                && str.charAt(pos) == delimiter
                && str.charAt(pos + 1) == ':') {
            if (++delimiter == 'D') { delimiter = 'A'; }
            return 2;
        }
        return 0;
    }
}

String[] strs = Splitter.split(question, matcher);

Then you implement the Splitter ... it must split the input at every position matches() returns a value greater than 0 and skipping the number of characters returned.

You can also improve the matcher to match blanks before the delimiter letter and after the ':' .