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Comparators

With the java.util.Comparator interface you can define an ordering for object instances of a given type. Unlike the java.lang.Comparable interface which is implemented by the sorted elements itself, Comparators are external and depending on the use case different orderings can be defined.

Since Java 8

import java.util.Collections; import java.util.Comparator; import java.util.List; public class Comparators { // There are pre-defined comparators in the Java API: static Comparator<String> c1 = String.CASE_INSENSITIVE_ORDER; // The natural ordering can be directly obtained with method references static Comparator<String> c2 = String::compareTo; // There is a factory method to compare on attributes static Comparator<String> c3 = Comparator.comparing(String::length); // Comparators can be reversed and chained static Comparator<String> c4 = Comparator // .comparing(String::length) // .reversed() // .thenComparing(String::compareToIgnoreCase); public static void main(String[] args) { var input = List.of("apple", "Cherry", "Fig", "Pear", "Mango"); // Sort the list with the different criteria: System.out.println(input.stream().sorted(c1).toList()); System.out.println(input.stream().sorted(c2).toList()); System.out.println(input.stream().sorted(c3).toList()); System.out.println(input.stream().sorted(c4).toList()); // Find the minimal element in respect to a Comparator: System.out.println(Collections.min(input, c4)); } }

This snippet at GitHub