Normalize All Whitespaces from a String in Java (Updated Website Post)

Overview

This post explains how to normalize and remove whitespace characters from strings in Java. Handling whitespace correctly is a common requirement in text processing and input validation, and Java provides multiple techniques depending on your goals — whether you want to trim spaces, remove all whitespace, or collapse multiple spaces into one.

Whitespace includes:

• Space characters
• Tabs (\t)
• Newlines (\n, \r)
• Other Unicode whitespace characters

Definitions

Whitespace normalization refers to:

• Removing unwanted whitespace at the beginning and end of a string
• Reducing multiple consecutive whitespace characters inside a string to a single space
  This improves consistency in text for comparison, storage, and display.

Using String Methods to Normalize Whitespace

Trim Leading and Trailing Whitespace

Java provides built-in methods to remove whitespace at the beginning and end of a string:

String input = "   Hello World   ";
String trimmed = input.trim(); // Removes leading and trailing spaces (ASCII)

If using Java 11 or later, prefer the Unicode-aware strip() method:

String stripped = input.strip();

• trim() removes only basic ASCII whitespace
• strip() removes all Unicode whitespace characters

Remove All Whitespace

To remove every whitespace character (spaces, tabs, newlines) from a string:

String noWhitespace = input.replaceAll("\\s", "");

• \\s in regex matches all whitespace characters
• This produces a string with no whitespace at all

Normalize Internal Spacing

If you want to collapse multiple internal whitespace characters into a single space while also trimming ends:

String normalized = input.strip()
                         .replaceAll("\\s+", " ");

This sequence:

1. Removes leading/trailing whitespace
2. Replaces one or more contiguous whitespace characters with a single space

Example:

String input = "  Hello   World   from   Java  ";
String normalized = input.strip()
                         .replaceAll("\\s+", " ");
// Result: "Hello World from Java"

Unicode-Aware White Space Handling

Starting with Java 11, strip(), stripLeading(), and stripTrailing() handle Unicode whitespace more comprehensively than the older trim() method.
Use these methods when dealing with international text or inputs from diverse sources.

Practical Example

public class WhitespaceExample {

    public static void main(String[] args) {
        String raw = "  Hello   World  \t from   Java  ";

        String trimmed = raw.strip();             // "Hello   World  \t from   Java"
        String noAllWhitespace = raw.replaceAll("\\s", ""); // "HelloWorldfromJava"
        String normalized = raw.strip().replaceAll("\\s+", " "); // "Hello World from Java"

        System.out.println("Trimmed: [" + trimmed + "]");
        System.out.println("No Whitespace: [" + noAllWhitespace + "]");
        System.out.println("Normalized: [" + normalized + "]");
    }
}

Choosing the Right Method