.replaceAll()

The String class’ .replaceAll() method replaces every matching subsequence in the input sequence with the specified replacement string.

string.replaceAll(String regex, String repl);

regex represents the regular expression: a set of special characters and letters used for matching specific text. repl represents the string to be substituted for each match.

Note: It’s important to note that certain characters in the replacement string, such as backslashes and dollar signs ($), may have special meanings, so it’s recommended to use Matcher.quoteReplacement(String) to prevent these characters from affecting the results.

Note: Both the .replace() and .replaceAll() methods replace all occurrences of a matching string and accept CharSequence as input. However, the key difference is that .replaceAll() treats the given CharSequence as a regular expression and searches for regex matches, while .replace() treats the input as plain text.

The example below removes all whitespace:

public class Main {
  public static void main(String[] args) {
    String myString = "Dog\t  \r\rComputer\n\n  \r House \t Yes \n  ";

    String regex = "\\s";
    // The shorthand code \s represents spaces, tabs, and newline characters
    String replacement = "";

    String newString = myString.replaceAll(regex, replacement);
    System.out.println(newString);

This results in the following output:

DogComputerHouseYes