java中关于method的基础编程

编写一个名为 vicDiff() 的方法，该方法接受两个整数值数组“ar1”和“ar2”，并返回一个整数 ArrayList。 该方法的代码应该在 ArrayList 中返回“ar1”中可以在“ar2”中找到的所有值。 如果输入数组“ar1”和“ar2”中的任何一个为空，则该方法应返回空。

import java.util.ArrayList;
import java.util.List;

class LabClass {

ArrayList<Integer> diff = new ArrayList<>();

public ArrayList<Integer> vicDiff(int ar1[], int ar2[]) {
    if (!(ar1 == null || ar2 == null)) {
        for (int i = 0; i < ar1.length; i++) {
            for (int j = 0; j < ar2.length; j++) {
                if (ar1[i] == ar2[j]) {
                    diff.add(ar1[i]);
                }
            }
        }
        return diff;
    } else {
        return null;
    }


}

}

public class Test {
public static void main(String[] args) {
int ar1[] = {1, 2, 3, 1, 5, 6, 7};
int ar2[] = {2, 9, 0, 4, 11, 1};
ArrayList arrayList;
LabClass labClass = new LabClass();

    arrayList = labClass.vicDiff(ar1, null);
    if (!(arrayList == null)) {
        for (Integer i :
                arrayList) {
            System.out.println(i);
        }
    }else{
        System.out.println("null");
    }
}

}

package com.csdn;

import java.util.ArrayList;

public class LabClass {

    public ArrayList<Integer> vicDiff(int ar1[], int ar2[]) {
        if (ar1 == null || ar1.length == 0 || ar2 == null || ar2.length == 0) {
            return null;
        }
        ArrayList<Integer> res = new ArrayList<>();
        for (int i = 0; i < ar1.length; i++) {
            for (int j = 0; j < ar2.length; j++) {
                if (ar1[i] == ar2[j]) {
                    res.add(ar1[i]);
                }
            }
        }
        return res;
    }

    public static void main(String[] args) {
        LabClass labClass = new LabClass();
        int ar1[] = { 1, 2, 3, 1, 5, 6, 7 };
        int ar2[] = { 2, 9, 0, 4, 11, 1 };
        System.out.println(labClass.vicDiff(ar1, ar2));
    }
}