Regular expression to return word present in the 1st enclosed parentheses.

Question

Example:

1. ((UINT32)((384UL*1024UL) - 1UL)) should return "UINT32"
2. (char)abc should return "char".
3. ((int)xyz) should return "int".

Answer 1

    Pattern p = Pattern.compile("\\(([^()]*)\\)");
    String[] tests = {
            "((UINT32)((384UL*1024UL) - 1UL))",
            "(char)abc",
            "((int)xyz)"
    };

    for (String s : tests) {
        Matcher m = p.matcher(s);
        if (m.find())
            System.out.println(m.group(1));
    }

Prints

UINT32
char
int

Explanation of the regular expression:

• \\( Start with a (
• ( start capturing group
• [^()]* anything but ( and ) 0 or more times
• ) end capturing group
• \\) end with a ).

---

Using regular expressions is a bit of an overkill though. You could also do

int close = s.indexOf(')');
int open = s.lastIndexOf('(', close);
result = s.substring(open+1, close);

Answer 2

Pattern p = Pattern.compile("\\(([^\\(\\)]+?)\\)");
Matcher m = p.matcher(input);
if (m.find())
  result = m.group(1);