Sort a single String in Java

java

sorting-algorithms

java-8

functional-programming

byNikita Barsukov·Nov 25, 2024

Quickly sort a String in Java by:

Converting it into a char array with yourString.toCharArray()
Sorting the array with the help of Arrays.sort(charArray)
Generating a sorted String from the array: new String(charArray)

char[] chars = "bac".toCharArray();
Arrays.sort(chars); // chars sorted in-place, no magic wand required ;)
String sorted = new String(chars); // Voila! "abc"

Handling character cases and special characters

Before employing Arrays.sort(), consider handling differences between uppercase and lowercase letters, along with any special characters:

char[] chars = yourString.toLowerCase().toCharArray(); 
Arrays.sort(chars); // Uniform case sorting
String sorted = new String(chars);

Optimizing string sorting for large inputs

For large strings, the approach above may run into performance issues. Dealing with these scenarios, Java Streams can be a silver bullet:

String sorted = yourString.chars() // Welcome to the world of parallel computing!
                           .sorted() // Sorting made easy
                           .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
                           .toString(); // Back to string-land!

Complex sorting requirements

Complex scenarios, like sorting considering locale differences or managing composite characters, often warrant using a Collator instance:

Collator collator = Collator.getInstance(Locale.US); // Hello, Uncle Sam!
String[] splitArray = yourString.split("");
Arrays.sort(splitArray, collator::compare); // Collator justifies its existence
String sorted = String.join("", splitArray);

Surrogate pairs and composite characters handling

Don't forget about surrogates pairs and composite characters when using the char data type—they're like those people at parties who always need extra attention:

// The construct for handling surrogate pairs
String sorted = yourString.codePoints() 
                           .sorted() 
                           .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
                           .toString();

Implementing custom sorting with insertion sort

Need customization? None of Java's built-in methods meet your conditions? No worries, you can implement your own insertion sort:

// PSEUDOCODE for insertion sort on a string
String sorted = insertionSortString(yourString); // Feel the power of hands-on sorting!

Tackling special input scenarios

Take into account various inputs like empty strings or special characters. They're the paradoxes of the sorting world:

if (yourString.isEmpty()) { 
    // What’s lighter than a feather? An empty string 😉
    return "";
}

if (yourString.matches("[^A-Za-z0-9]+")) {
    // Special characters can be sorted too, just not alphabetically
    return yourString;
}

Stream-based approach for string sorting

For a slightly different approach, let's use Java's Streams and their functional programming features:

String sorted = Stream.of(yourString.split("")) // Divide and conquer!
                      .sorted() // No sweat sorting
                      .collect(Collectors.joining()); // The Reunion!

Optimization and efficiency gains

It’s all about maximizing efficiency—handling accented characters, dealing with special cases, and caching Collator objects:

if (collatorMap.containsKey(languageTag)) {
     collatorMap.get(languageTag); // Once created, forever retrieved
} else {
     Collator c = Collator.getInstance(Locale.forLanguageTag(languageTag));
     collatorMap.put(languageTag, c);
     c // This Collator instance will serve many strings, efficiency at its finest!
}