// Compile and use regular expression
Pattern pattern = Pattern.compile(patternStr);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.find();

if (matchFound) {
    // Get all groups for this match
    for (int i=0; i<=matcher.groupCount(); i++) {
        String groupStr = matcher.group(i);
        System.out.println(groupStr);
    }
}

// Compile and use regular expression
RegExp regExp = RegExp.compile(patternStr);
MatchResult matcher = regExp.exec(inputStr);
boolean matchFound = matcher != null; // equivalent to regExp.test(inputStr);

if (matchFound) {
    // Get all groups for this match
    for (int i = 0; i < matcher.getGroupCount(); i++) {
        String groupStr = matcher.getGroup(i);
        System.out.println(groupStr);
    }
}

private ArrayList<String> getMatches(String input, String pattern) {
    ArrayList<String> matches = new ArrayList<String>();
    RegExp regExp = RegExp.compile(pattern, "g");
    for (MatchResult matcher = regExp.exec(input); matcher != null; matcher = regExp.exec(input)) {
       matches.add(matcher.getGroup(0));
    }
    return matches;
}

ArrayList<String> matches = getMatches(someInputStr, "\$\{[A-Za-z_0-9]+\}");
for (int i = 0; i < matches.size(); i++) {
    String match = matches.get(i);

}