朴素的方法，代码反而更难 
import java.util.*;

public class Main{
        public static void main(String[] args){
            Scanner scanner = new Scanner(System.in);
            while(scanner.hasNext()){
                int N = scanner.nextInt();
                List<Integer> list = new ArrayList<>(N);
                for (int i = 0; i < N; i++) {
                    int var = scanner.nextInt();
                    if(!list.contains(var)){
                        list.add(var);
                    }
                }
                list.sort(new Comparator<Integer>() {
                    @Override
                    public int compare(Integer o1, Integer o2) {
                        return o1.compareTo(o2);
                    }
                });
                Object[] objects = list.toArray();
                for(Object object : objects){
                    System.out.println(object);
                }
            }
        }
}