如何在正则表达式中使用组在java中？

Question

I have this code and I want to find both 1234 and 4321 but currently I can only get 4321. How could I fix this problem?

String a = "frankabc123 1234 frankabc frankabc123 4321 frankabc";
String rgx = "frank.* ([0-9]*) frank.*";
Pattern patternObject = Pattern.compile(rgx);
Matcher matcherObject = patternObject.matcher(a);
while (matcherObject.find()) {
    System.out.println(matcherObject.group(1));
}

Answer 1

Your regex is too greedy. Make it non-greedy.

String rgx = "frank.*? ([0-9]+) frank";

Answer 2

Your re is incorrect. The first part: frank.* matches everything and then backtracks until the rest of the match succeeds. Try this instead:

String rgx = "frank.*? ([0-9]*) frank";

The ? after the quantifier will make it reluctant, matching as few characters as necessary for the rest of the pattern to match. The trailing .* is also causing problems (as nhahtdh pointed out in a comment).