How to Split String Using Regex in Java: Simple Guide

In Java, you can split a string using regex by calling split() method on a string object with a regex pattern as the argument. For example, str.split("\\s+") splits the string at one or more whitespace characters.

Syntax

The basic syntax to split a string using regex in Java is:

String[] parts = inputString.split("regexPattern");

Here:

• inputString is the string you want to split.
• regexPattern is the regular expression defining where to split.
• The method returns an array of strings split at matches of the regex.

java

String[] parts = inputString.split("regexPattern");

Example

This example shows how to split a sentence into words using whitespace as the separator with regex "\\s+" which means one or more spaces.

java

public class SplitExample {
    public static void main(String[] args) {
        String sentence = "Java is fun to learn";
        String[] words = sentence.split("\\s+");
        for (String word : words) {
            System.out.println(word);
        }
    }
}

Output

Java
is
fun
to
learn

Common Pitfalls

Common mistakes include:

• Not escaping special regex characters properly (like dot . or backslash \\).
• Using split(".") which splits at every character because dot means any character in regex.
• Expecting split() to remove empty strings when delimiters are adjacent (it keeps empty strings unless you limit the result).

Correct usage requires escaping special characters with double backslashes.

java

public class SplitPitfall {
    public static void main(String[] args) {
        String data = "one.two.three";
        // Wrong: splits at every character because '.' means any char
        String[] wrong = data.split(".");
        System.out.println("Wrong split length: " + wrong.length);

        // Right: escape dot to split at literal '.'
        String[] right = data.split("\\.");
        System.out.println("Right split length: " + right.length);
    }
}

Output

Wrong split length: 0
Right split length: 3

Quick Reference

• split(regex): splits string by regex, returns array.
• Escape special chars: use double backslash \\ for regex metacharacters.
• Limit parameter: split(regex, limit) controls max splits and trailing empty strings.

Key Takeaways

Use split() method with a regex string to split Java strings by patterns.

Always escape regex special characters with double backslashes in Java strings.

Regex like "\\s+" splits on one or more whitespace characters.

Beware that split(".") splits at every character because dot means any character.

Use the optional limit parameter to control the number of splits and handle empty strings.