7-3 求集合交集 (20 分)jaav版

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n1 = sc.nextInt();
        int n2 = sc.nextInt();
        int a[] = new int[n1];
        for (int i = 0; i < n1; i++) {
            a[i] = sc.nextInt();
        }
        ArrayList alB = new ArrayList();
        for (int i = 0; i < n2; i++) {
            alB.add(sc.nextInt());
        }
        String sum = "";
        for (int i = 0; i < n1; i++) {
            if (alB.contains(a[i])) {
                sum += (a[i] + " ");
            }
        }
        if (sum.equals("")) {
            System.out.println("NULL");
        } else {
            System.out.println(sum.substring(0, sum.length() - 1));
        }
    }
}