how to replace multiple matched Regex

Question

I have a set of regex replacements that are needed to be applied to a set of String,

For example:

1. all multiple spaces with single space (\"\\s{

Answer 1

You have these 2 replaceAll calls:

s = s.replaceAll("\\s{2,}"," ");
s = s.replaceAll("\\.([a-zA-Z])",". $1");

You can combine them into a single replaceAll like this:

s = s.replaceAll("\\s{2,}|(\\.)(?=[a-zA-Z])", "$1 ");

RegEx Demo

Answer 2

Look at Replace multiple substrings at Once and modify it.

Use a Map<Integer, Function<Matcher, String>>.

• group numbers as Integer keys
• Lambdas as values

Modify the loop to check which group was matched. Then use that group number for getting the replacement lambda.

Pseudo code

Map<Integer, Function<Matcher, String>> replacements = new HashMap<>() {{
    put(1, matcher -> "");
    put(2, matcher -> " " + matcher.group(2));
}};

String input = "lorem substr1 ipsum substr2 dolor substr3 amet";

// create the pattern joining the keys with '|'. Need to add groups for referencing later
String regexp = "(\\s{2,})|(\\.(?:[a-zA-Z]))";

StringBuffer sb = new StringBuffer();
Pattern p = Pattern.compile(regexp);
Matcher m = p.matcher(input);

while (m.find()) {
    //TODO change to find which groupNum matched
    m.appendReplacement(sb, replacements.get(m.group(groupNum)));
}
m.appendTail(sb);


System.out.println(sb.toString());   // lorem repl1 ipsum repl2 dolor repl3 amet