How does the replaceAll java method work?

Question

I'm trying to figure out how the str.replaceAll(string, newString) method works. I know how to use it, but I'm trying to figure out what goes on inside the method. Does it use multiple for loops and strings, or something more advanced than that? Ideas, pseudocode, and code examples would be lovely.

PS I've already searched this up, but it only shows how to use it, not how it works.

Related: https://stackoverflow.com/questions/261015/where-can-i-see-the-source-code-of-the-sun-jdk — Michael Butscher, Nov 20 '18 at 22:59
Pore over the source code of `String#replaceAll`, debug some places to figure it out :) — Andrew Tobilko, Nov 20 '18 at 23:00
I you use an IDE you can easily see the code, LIke with intelliJ with press `ctrl` and click on the method name to see the implementation — azro, Nov 20 '18 at 23:02
@azro - you can also just middle-click on any object, method, etc. — Zephyr, Nov 20 '18 at 23:03
@Zephyr not sure we need to discuss all shorcut that exists ^^ :D — azro, Nov 20 '18 at 23:03
Just expanding upon yours, that's all. I was quite happy when I first found out :P — Zephyr, Nov 20 '18 at 23:05

GBlodgett · Answer 1 · 2018-11-20T23:11:28.987

According to the source code for String#replaceAll:

public String replaceAll(String regex, String replacement) {
    return Pattern.compile(regex).matcher(this).replaceAll(replacement);
}

It creates a Pattern and uses regex to replace the target with the replacement.

In case you want to know about the Matcher#replaceAll call:

public String replaceAll(String replacement) {
    reset();
    boolean result = find();
    if (result) {
        StringBuffer sb = new StringBuffer();
        do {
            appendReplacement(sb, replacement);
            result = find();
        } while (result);
        appendTail(sb);
        return sb.toString();
    }
    return text.toString();
}

How does the replaceAll java method work?

1 Answers1