获取String.replaceAll（）删除的内容

Question

So, let's say I got my regular expression

String regex = "\d*";

for finding any digits.

Now I also got a inputted string, for example

String input = "We got 34 apples and too much to do";

Now I want to replace all digits with "", doing it like that:

input = input.replaceAll(regex, "");

When now printing input I got "We got apples and too much to do". It works, it replaced the 3 and the 4 with "".

Now my question: Is there any way - maybe an existing lib? - to get what actually was replaced?

The example here is very simple, just to understand how it works. Want to use it for complexer inputs and regex.

Thanks for your help.

Answer 1

You can use a Matcher with the append-and-replace procedure:

String regex = "\\d*";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);

StringBuffer sb = new StringBuffer();
StringBuffer replaced = new StringBuffer();
while(matcher.find()) {
    replaced.append(matcher.group());
    matcher.appendReplacement(sb, "");
}
matcher.appendTail(sb);

System.out.println(sb.toString());  // prints the replacement result
System.out.println(replaced.toString()); // prints what was replaced