Java .replaceAll()

The .replaceAll() method replaces every match of a specified regular expression with a given string.

Syntax

string.replaceAll(regex, repl);

• regex: A string that defines the regular expression pattern.
• repl: The string that will replace every occurrence of the pattern found in the original string.

Note: If the objective is to search and replace a sequence of plain text without using a regex pattern, use the .replace() method.

Example

The example below sanitizes a user inputted phone number by removing any non-digit characters:

public class Main {
  public static void main(String[] args) {
    String phoneNumber = "(123) 456-7890";
    String sanitizedPhoneNumber = sanitizePhoneNumber(phoneNumber);
    System.out.println(sanitizedPhoneNumber);
  }
  public static String sanitizePhoneNumber(String number) {
    return number.replaceAll("[^0-9]", "");
  }
}

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Note: When using regex metacharacters (e.g. .,*,+,?,^,$,\\) in the repl string, use Matcher.quoteReplacement(String) to ensure they are interpreted literally.

In this example, sanitizePhoneNumber is a method that takes a phone number and removes any non-digit characters. In the replaceAll() method, the [^0-9] pattern is passed for the regex argument and "" for the repl argument. This means that every non-digit character will be replaced with an empty string. Then the sanitized phone number is printed to the console:

1234567890

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