How to remove line breaks from a file in Java?

The Immutable Truth: Strings in Java

In Java, reality can be quite stubborn - Strings are immutable. This means they resist change, like your grandparents refusing to use smartphones. So, whenever you're removing line breaks or doing any form of string manipulation, remember to reassign the transformed string:

String content = Files.readString(Paths.get("yourfile.txt"));
// Gramps won't text, but he might be enticed to send Morse code!
content = content.replace("\n", "").replace("\r", "");
Files.writeString(Paths.get("yourfile.txt"), content);


Cross-platform Line Breaks: Java Universal Translator

Java is experienced in diplomacy. It offers you System.getProperty("line.separator") to keep your code friendly across platforms. With this, you get 'the right kind of line-break, for the right type of occasion':

String newline = System.getProperty("line.separator");
String content = Files.readString(Paths.get("yourfile.txt"));
// Java, the Switzerland of coding languages
content = content.replace(newline, "");
Files.writeString(Paths.get("yourfile.txt"), content);


Caught in the Net: Use Regex for More Efficiency

When you're up against line breaks of multiple types, regular expressions invite you to a more efficient way of handling them all in one go:

String content = Files.readString(Paths.get("yourfile.txt"));
// Regex, the Swiss Army knife of coders vs. line breaks.
content = content.replaceAll("\\r\\n|\\r|\\n", "");
Files.writeString(Paths.get("yourfile.txt"), content);


Avoid Concatenation Catastrophes with Spaces

Line breaks often separate words that should stay separated. Replacing line breaks with a space rather than an empty string can help you avoid unintended, and often hilarious, word concatenations:

String content = Files.readString(Paths.get("yourfile.txt"));
// Bet you've never seen a space fight off potential catastrophe so effectively!
content = content.replaceAll("\\R+", " ");
Files.writeString(Paths.get("yourfile.txt"), content);


Bring in the External Reinforcements: Apache Commons Lang

There are certain situations so complex or so tedious that even Java admits it needs reinforcement. Behold the Apache Commons Lang with its StringUtils.normalizeSpace method that quickly and elegantly normalizes all white spaces:

// It's the cavalry! The Apache Commons Lang cavalry, that is.
String content = FileUtils.readFileToString(new File("yourfile.txt"), Charset.defaultCharset());
content = StringUtils.normalizeSpace(content);
FileUtils.writeStringToFile(new File("yourfile.txt"), content, Charset.defaultCharset());


This certainly simplifies the process, but remember to wave the Apache Commons Lang flag in your project libraries.

Aim for Perfection (and more StackOverflow votes... not that it matters)

Removing line breaks may seem like a breeze, but tackling it effectively requires attentive thought and planning:

• Use line.separator to maintain OS compatibility, like maintaining peace between Star Trek and Star Wars fans.
• Guard against the creation of Frankenstein words—substitute line breaks with a space when needed.
• Regular expressions offer versatility when dealing with a wide range of whitespace characters.
• Working with large files? Process them line by line with buffered streams to avoid choking your CPU with an Moby Dick-like book.
• Be aware of how file encoding differences can interpret line breaks and characters. A seemingly harmless text file can turn into a foul beast with bad encoding!