Regex : matches all 7 digit number except the one that starts with abc

You can use

\b(?<!abc:)\d{7}\b
(?<!\d)(?<!abc:)\d{7}(?!\d)

See the regex demo.

Details:

• \b - word boundary ((?<!\d) makes sure there is no other digit immediately to the left of the current location)
• (?<!abc:) - a negative lookbehind that fails the match if there is abc: immediately to the left of the current location
• \d{7} - seven digits
• \b - word boundary ((?!\d) makes sure there is no other digit immediately to the right of the current location).

See the Java demo:

String s = "abc:1234567,cd:2345678,efg:3456789012";
Pattern pattern = Pattern.compile("\\b(?<!abc:)\\d{7}\\b");
Matcher matcher = pattern.matcher(s);
while (matcher.find()){
    System.out.println(matcher.group());  // => 2345678
}