Regular expression - capture groups

[Bruce Jin]

I have this code:

    
Pattern pat = Pattern.compile("\\Q${\\E.*}");// for ${.*} 
String input = "123 ${abc} 456 ${xyz} abc ";
Matcher matcher = pat.matcher(input);
 
while (matcher.find()) {
  int start = matcher.start();
  int end = matcher.end();
  System.out.println("start=" + start + ", end=" + end
+ ",   match string=" + input.substring(start, end));
}

I expect it to print 2 lines:

start=4, end=8, match string=${abc}
start=15, end=19, match string=${xyz}

But it acctually prints only 1 line:

start=4, end=21, match string=${abc} 456 ${xyz}

Why?
Thanks.

[Ernest Friedman-Hill]

Because regular expressions as "greedy" and match as much as possible by default. Your ".*" in the braces matches any character, so the first close brace is matched as part of the contents inside the braces.

There are a number of ways to fix this; one would be to use "[^}]*" instead of ".*".

[Bruce Jin]

Thanks.
"[^}]*" instead of ".*" fixed it.