ইমিউটেবল (Immutable) লিস্ট তৈরি

Map<String, Integer> map = new HashMap<>();
map.put("a", 1);
map.put("b", 2);
map.put("c", 3);
map = Collections.unmodifiableMap(map);

Set<String> set =
    Collections.unmodifiableSet(
        new HashSet<>(
            Arrays.asList("a", "b", "c")
        )
    );

// Get last element
var last = list.get(list.size() - 1);
// Get first
var first = list.get(0);
// Reverse iteration: manual