Different Ways of Sorting a List of Items in Java

Programming & Development / April 16, 2025

Different Ways of Sorting a List of Items in Java

java list sorting comparable comparator java 8 streams lambda expressions collections sort custom sorting sort list java java programming stream api tree set priority queue java functional programming

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Sorting lists is a routine but essential task in Java development. Whether you're arranging names alphabetically or sorting objects based on multiple attributes, Java provides several powerful mechanisms to perform sorting. Let’s explore various ways to sort a List in Java.

✅ 1. Using `Collections.sort()` with `Comparable`

The classic way for sorting a list of elements that implement the Comparable interface.

java

Collections.sort(list);

✅ 2. Using `Collections.sort()` with `Comparator`

When you want a custom sort without changing the model class:

java

Collections.sort(list, Comparator.comparing(MyClass::getSomeProperty));

✅ 3. Using `List.sort()` (Java 8+)

This is a cleaner approach added in Java 8:

java

list.sort(Comparator.comparing(MyClass::getSomeProperty));

✅ 4. Using Java Streams

Create a sorted copy without mutating the original list:

java

List<MyClass> sorted = list.stream()
    .sorted(Comparator.comparing(MyClass::getSomeProperty))
    .collect(Collectors.toList());

✅ 5. Sorting with Multiple Conditions

Use thenComparing to handle complex sorting logic:

java

list.sort(
    Comparator.comparing(MyClass::getPriority)
              .thenComparing(MyClass::getTimestamp)
);

✅ 6. Descending Order

Use reversed():

java

list.sort(Comparator.comparing(MyClass::getScore).reversed());

✅ 7. Using `TreeSet` for Sorting with Uniqueness

Automatically sorted collection with no duplicates:

java

Set<String> sortedSet = new TreeSet<>(list);

You can also define a custom comparator:

java

Set<Person> sortedByName = new TreeSet<>(Comparator.comparing(Person::getName));
sortedByName.addAll(personList);

✅ 8. Using `PriorityQueue` (Heap Sort Behavior)

Useful when you need sorted extraction one by one:

java

PriorityQueue<Integer> pq = new PriorityQueue<>(list);
while (!pq.isEmpty()) {
    System.out.println(pq.poll()); // retrieves in sorted order
}

✅ 9. Using `Arrays.sort()` with Conversion

For quick sort on a fixed-size list:

java

String[] arr = list.toArray(new String[0]);
Arrays.sort(arr);
List<String> sortedList = Arrays.asList(arr);

✅ 10. Sorting Using Custom Functional Utilities

If you often sort by dynamic fields, utility methods help:

java

public static <T, U extends Comparable<? super U>> void sortByField(List<T> list, Function<T, U> keyExtractor) {
    list.sort(Comparator.comparing(keyExtractor));
}

// Usage:
sortByField(personList, Person::getAge);

✅ 11. Sorting with Guava or Apache Commons

If you're using libraries like Guava or Apache Commons Collections, they offer utilities like:

java

Ordering<Person> byName = Ordering.natural().onResultOf(Person::getName);
List<Person> sorted = byName.sortedCopy(personList);

✅ 12. Sorting Immutable Lists (Java 10+)

Create sorted copies using List.copyOf() or Collectors.toUnmodifiableList():

java

List<String> sorted = list.stream()
    .sorted()
    .collect(Collectors.toUnmodifiableList());

Conclusion

From simple one-liners to advanced functional techniques, Java offers many options for sorting. Choosing the right approach depends on whether you want mutability, performance, readability, or stream-processing style. For most modern applications, the combination of Comparator.comparing(), lambdas, and streams provides the most expressive and clean syntax.

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