Try It Yourself - SyntaxStudy Editor

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import java.util.*;

public class TreeMapSortDemo {
    public static void main(String[] args) {
        // --- TreeMap (sorted by key) ---
        TreeMap<String, Integer> population = new TreeMap<>();
        population.put("Tokyo",    14000000);
        population.put("New York",  8000000);
        population.put("London",    9000000);
        population.put("Berlin",    3700000);

System.out.println("Sorted map: " + population);
        System.out.println("First key:  " + population.firstKey());
        System.out.println("Last key:   " + population.lastKey());
        System.out.println("Head map (< London): " + population.headMap("London"));

// --- Sorting a List with Comparator ---
        List<String> names = new ArrayList<>(Arrays.asList(
            "Charlie", "Alice", "Bob", "Dave"
        ));

Collections.sort(names); // natural order
        System.out.println("
Natural sort: " + names);

names.sort(Comparator.comparingInt(String::length)
                             .thenComparing(Comparator.naturalOrder()));
        System.out.println("By length, then alpha: " + names);

// --- Collections utilities ---
        System.out.println("Min: " + Collections.min(names));
        System.out.println("Max: " + Collections.max(names));
        Collections.reverse(names);
        System.out.println("Reversed: " + names);
    }
}