Regular Expressions

Code

import java.util.regex.*;

String text = "Phone: 138-1234-5678, Email: [email protected]";

// Find
Pattern phonePattern = Pattern.compile("\d{3}-\d{4}-\d{4}");
Matcher matcher = phonePattern.matcher(text);
if (matcher.find()) {
    System.out.println("Phone: " + matcher.group());
}

// Replace
String result = text.replaceAll("\d", "*");

// Split
String[] parts = "a,b,,c".split(",");

// Validate
boolean isValid = "[email protected]".matches(
    "[\w.]+@[\w.]+\.\w+");

// Named capture group
Pattern p = Pattern.compile("(?<year>\d{4})-(?<month>\d{2})");
Matcher m = p.matcher("2024-01");
if (m.find()) {
    System.out.println(m.group("year"));
    System.out.println(m.group("month"));
}

Explanation

Pattern compiles regex; Matcher performs matching, searching, and replacement.

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