java regular expression find and replace

Question

I am trying to find environment variables in input and replace them with values.

The pattern of env variable is ${\\\\.}

Pattern myPatte         


        

Answer 1

You can use a StringBuffer in combination with the Matcher appendReplacement() method, but if the the pattern does not match, there is no point in creating the StringBuffer.

For example, here is a pattern that matches ${...}. Group 1 is the contents between the braces.

static Pattern rxTemplate = Pattern.compile("\\$\\{([^}\\s]+)\\}");

And here is sample function that uses that pattern.

private static String replaceTemplateString(String text) {
    StringBuffer sb = null;
    Matcher m = rxTemplate.matcher(text);
    while (m.find()) {
        String t = m.group(1);
        t = t.toUpperCase(); // LOOKUP YOUR REPLACEMENT HERE

        if (sb == null) {
            sb = new StringBuffer(text.length());
        }
        m.appendReplacement(sb, t);
    }
    if (sb == null) {
        return text;
    } else {
        m.appendTail(sb);
        return sb.toString();
    }
}