I've been trying to devise a method of replacing multiple String#replaceAll calls with a Pattern/Matcher instance in the hopes that it would be faster than my current method of replacing text in a String, but I'm not sure how to go about it.
Here is an example of a String that I want to manipulate:
@bla@This is a @red@line @bla@of text.
As you can see, there are multiple @ characters with 3 characters in between; this will always be the case. If I wanted to replace every instance of '@xxx@' (where xxx can be any lowercase letter or digit from 0 to 9), what would the most efficient way to go about it be? Currently I'm storing a Map where its keys are '@xxx@' substrings, and the values are what I want to replace that specific substring with; I check if the whole String contains the '@xxx@' substring, and call a replaceAll method for each instance, but I imagine this is pretty inefficient.
Thank you very much!
TL;DR - Would a Pattern/Matcher to replace a substring of a String with a different String be more efficient than checking if the String contains the substring and using String#replaceAll? If so, how would I go about it?
This is a relatively straightforward case for appendReplacement:
// Prepare map of replacements
Map<String,String> replacement = new HashMap<>();
replacement.put("bla", "hello,");
replacement.put("red", "world!");
// Use a pattern that matches three non-@s between two @s
Pattern p = Pattern.compile("@([^@]{3})@");
Matcher m = p.matcher("@bla@This is a @red@line @bla@of text");
StringBuffer sb = new StringBuffer();
while (m.find()) {
// Group 1 captures what's between the @s
String tag = m.group(1);
String repString = replacement.get(tag);
if (repString == null) {
System.err.println("Tag @"+tag+"@ is unexpected.");
continue;
}
// Replacement could have special characters, e.g. '\'
// Matcher.quoteReplacement() will deal with them correctly:
m.appendReplacement(sb, Matcher.quoteReplacement(repString));
}
m.appendTail(sb);
String result = sb.toString();