String replaceAll()

The Java replaceAll() method is a part of the java.lang.String class, and it is used to replace all occurrences of a specified substring (or regular expression) in the original string with a new string. It returns a new string with all replacements applied while leaving the original string unchanged. The basic syntax of the replaceAll() method is as follows:

String replacedString = originalString.replaceAll(regex, replacement);

• originalString: The original string in which you want to perform replacements.
• regex: A regular expression or a plain substring to be searched for and replaced.
• replacement: The string that will replace the matched substring or regular expression.

Here’s a simple example demonstrating the use of replaceAll() to replace all occurrences of a substring in a string:

public class StringReplaceAllExample {
    public static void main(String[] args) {
        String originalString = "The quick brown fox jumps over the lazy dog.";
        String replacedString = originalString.replaceAll("fox", "cat");

        System.out.println("Original String: " + originalString);
        System.out.println("Replaced String: " + replacedString);
    }
}

In this example, the replaceAll() method is used to replace all occurrences of the substring “fox” with “cat” in the originalString. The original string remains unchanged, and the modified string is stored in replacedString.

Keep in mind that the first argument, regex, can also be a regular expression pattern. For example, if you want to replace all digits in a string with “X”, you can use a regular expression like this:

String originalString = "123-456-7890";
String replacedString = originalString.replaceAll("\\d", "X");

The regular expression \\d matches all digits, and they are replaced with “X”. The \\ is an escape character in Java, and it’s used to represent a single backslash in the regular expression pattern.