Cookbooks
Java
Chapter 2. Strings
Deleting characters matching a pattern

Java:
Deleting characters matching a pattern

How to:

In Java, we often use the String.replaceAll() method with a regex pattern to delete characters. Here’s a quick example:

public class PatternDeletionExample {
    public static void main(String[] args) {
        String originalString = "Hello, 123 World! This-is a test-string.";
        String pattern = "\\d|-"; // \d is a digit, - is a literal dash

        String cleanedString = originalString.replaceAll(pattern, "");
        System.out.println(cleanedString); // Prints: Hello,  World! This is a teststring.
    }
}

This code snips out digits and dashes to tidy up our string.

Deep Dive

Way back when, folks manipulated strings without handy methods and regex. They did it the hard way, char by char, which was a pain. Then regular expressions (regex) came along, and things got a whole lot easier. Regex is a powerful pattern-matching standard used in text processing.

So why replaceAll()? It’s part of the String class in Java, and since strings are everywhere, it became the go-to for pattern-based text modding. It takes two params: the regex for the pattern to nix and what to slap in its place—in our case, an empty string to delete it.

There are alternatives like Pattern and Matcher classes for more complex work. These come in handy for more nuanced tasks, like finding patterns without deleting them, or replacing them in more intricate ways.

The implementation hinges on the Java regex engine, which parses the pattern and applies it to the target string. It’s a mini search-and-destroy mission for characters—find the pattern, then zap it.

See Also

Converting a string to lower caseExtracting substrings