String.replaceAll() is a method that accepts a regex string, and replaces all occurrences of the regex with the provided replacement string.

If you are only trying to replace a specific substring and not a more general pattern, it will be better to use String.replace() instead.

String.replaceAll() internally compiles the given regex string and then replaces all instances of the resulting Pattern with the replacement string. Using replaceAll() with a pattern string that contains no special characters (e.g. "abc", or "good bye") will cause a regex to be compiled unnecessarily. The same result could be achieved by just performing simpler string comparisons using String.replace() instead.

Only use String.replaceAll() if you require complex regex pattern matching.

Bad Practice

String s = "Tha quick brown fox jumped over tha lazy dog.";

s.replaceAll("tha", "the"); // Unnecessary regex compilation

Recommended

String.replace() does not compile a regex when replacing instances of the given substring.

s.replace("tha", "the");

Exceptions

If you are indeed trying to match a specific regex based pattern, feel free to disregard this occurrence.

References

Java 8 JavaDocs - String.replace()
Java 8 JavaDocs - String.replaceAll()

Glowman554 / BetterNudel

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