Question

I have the following string:

<div height="40px" width="30px" />

I would like to replace with regex all the numbers that have px after them with X times their values. (X is a variable).

So if X=3, the result will be

<div height="120px" width="90px" />

Please note that X must be a variable that I will retrieve to the function

Answer 1

The following code will replace 30px with 240px in the String s using regular expressions:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Example {
    public static void main(String[] args) {
        String s = "abc 30px def";
        int var = 8;

        Pattern patt = Pattern.compile("([0-9]+)px");
        Matcher m = patt.matcher(s);
        StringBuffer sb = new StringBuffer(s.length());
        while (m.find()) {
            int px = Integer.parseInt(m.group(1));
            String next = String.valueOf(var * px) + "px";
            m.appendReplacement(sb, Matcher.quoteReplacement(next));
        }
        m.appendTail(sb);
        System.out.println(sb.toString());
    }
}

Here are the steps it performs:

• Create a compiled regular expression. This improves performance when a regular expression is used again later.
• Search the string s for matches and for each match:
  • Convert the string to integer and multiple it by var.
  • Append px again and pass it as a replacement string.
• Finally, print the input string again with certain strings replaced.