三种解法

import java.util.*;

public class Main {
    public static void main(String[] args) {
        solution1();
        solution2();
        solution3();
    }

    static void solution1() {
        Scanner in = new Scanner(System.in);
        in.nextInt();
        boolean[] arr = new boolean[501];
        while (in.hasNextInt()) {
            arr[in.nextInt()] = true;
        }
        for (int i = 1; i < arr.length; i++) {
            if (arr[i]) {
                System.out.println(i);
            }
        }
    }

    static void solution2() {
        Scanner in = new Scanner(System.in);
        in.nextInt();
        BitSet bitset = new BitSet();
        Queue<Integer> pq = new PriorityQueue<Integer>();
        while (in.hasNextInt()) {
            int val = in.nextInt();
            if (!bitset.get(val)) {
                bitset.set(val);
                pq.offer(val);
            }
        }
        while (!pq.isEmpty()) {
            System.out.println(pq.poll());
        }
    }

    static void solution3() {
        Scanner in = new Scanner(System.in);
        in.nextInt();
        TreeSet set = new TreeSet();
        while (in.hasNextInt()) {
            set.add(in.nextInt());
        }
        set.forEach(System.out::println);
    }
}