Question

Matcher matcher = Pattern.compile("\\bwidth\\s*:\\s*(\\d+)px|\\bbackground\\s*:\\s*#([0-9A-Fa-f]+)").matcher(myString);
if (matcher.find()) {
    System.out.println(matcher.group(2));
}

Example data:
myString = width:17px;background:#555;float:left; will produce null.
What I wanted:

matcher.group(1) = 17
matcher.group(2) = 555

I’ve just started using regex on Java, any help?

Answer 1

I would suggest to split things a bit up.

Instead of building one large regex (maybe you want to add more rules into the String?) you should split up the string in multiple sections:

String myString = "width:17px;background:#555;float:left;";
String[] sections = myString.split(";"); // split string in multiple sections
for (String section : sections) {

  // check if this section contains a width definition
  if (section.matches("width\\s*:\\s*(\\d+)px.*")) {
    System.out.println("width: " + section.split(":")[1].trim());
  }

  // check if this section contains a background definition
  if (section.matches("background\\s*:\\s*#[0-9A-Fa-f]+.*")) {
    System.out.println("background: " + section.split(":")[1].trim());
  }

  ...
}