Pattern & Matcher in Java

From the Java cheat sheet · Regular Expressions · verified Jul 2026

Pattern & Matcher

Java regex via String helpers and the Pattern/Matcher API.

java

// Quick Reference
"abc123".matches("[a-z]+\\d+");     // true (whole string)
"a1b2".replaceAll("\\d", "#");       // "a#b#"
"a,b;c".split("[,;]");               // ["a", "b", "c"]

💡 In Java source, regex backslashes are doubled: \d for a digit, \s for whitespace.

⚡ String.matches() must match the ENTIRE string; Matcher.find() matches any substring.

📌 Compile a Pattern once and reuse it in loops - compiling is relatively expensive.

🟢 Groups are 1-indexed; group(0) (or group()) is the full match.

regexpattern

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