import java.util.*;

/** JEP 431 (final): SequencedCollection, SequencedSet, SequencedMap. */
public class SequencedCollectionsDemo {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>(List.of("a", "b", "c"));
        System.out.println("getFirst/getLast: " + list.getFirst() + " " + list.getLast());
        System.out.println("reversed view   : " + list.reversed());
        list.addFirst("z"); list.removeLast();
        System.out.println("addFirst+removeLast: " + list);

        LinkedHashSet<Integer> set = new LinkedHashSet<>(List.of(1, 2, 3));
        System.out.println("LinkedHashSet reversed: " + set.reversed());

        LinkedHashMap<String, Integer> map = new LinkedHashMap<>();
        map.put("x", 1); map.put("y", 2); map.put("z", 3);
        System.out.println("firstEntry/lastEntry : " + map.firstEntry() + " " + map.lastEntry());
        map.putFirst("w", 0);
        System.out.println("putFirst        : " + map);
        System.out.println("reversed map    : " + map.reversed());

        // reversed() is a view, not a copy
        List<String> src = new ArrayList<>(List.of("1", "2")); List<String> rev = src.reversed(); src.add("3");
        System.out.println("view sees add   : " + rev);

        try { List.of(1, 2).addFirst(0); } catch (UnsupportedOperationException e) { System.out.println("immutable list : UnsupportedOperationException"); }
        try { new HashSet<>(List.of(1)).getClass().getMethod("getFirst"); } catch (NoSuchMethodException e) { System.out.println("HashSet         : no getFirst (unordered)"); }
    }
}