(合并两个列表)使用下面的方法头编写一个方法，返回两个数组列表的并集。 publ ic static ArrayList<Integer> union( ArrayList<Integer> listl, ArrayList<Integer> list2) 例如，两个数组列表｛2，3，1，5｝和｛3，4，6｝的并集为｛2，3，1，5，3，4，6｝编写测试程序，提示用户输入两个列表，每个列表有5个整数，然后显示它们的并集。输出中，以一个空格进行分隔。下面是一个运行示例： Enter five integers for list1: 3 5 45 4 3 Enter five integers for list2: 33 51 5 4 13 The combined list is 3 5 45 4 3 33 51 5 4 13

以下是实现上述功能的 Java 代码：

import java.util.ArrayList;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // Prompt the user to enter two lists
        System.out.print("Enter five integers for list1: ");
        ArrayList<Integer> list1 = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            list1.add(input.nextInt());
        }

        System.out.print("Enter five integers for list2: ");
        ArrayList<Integer> list2 = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            list2.add(input.nextInt());
        }

        // Find the union of the two lists
        ArrayList<Integer> unionList = union(list1, list2);

        // Display the combined list
        System.out.print("The combined list is ");
        for (int i = 0; i < unionList.size(); i++) {
            System.out.print(unionList.get(i) + " ");
        }
    }

    public static ArrayList<Integer> union(ArrayList<Integer> list1, ArrayList<Integer> list2) {
        ArrayList<Integer> unionList = new ArrayList<>();

        // Add elements of list1 to the union list
        for (int i = 0; i < list1.size(); i++) {
            unionList.add(list1.get(i));
        }

        // Add elements of list2 to the union list if they are not already in it
        for (int i = 0; i < list2.size(); i++) {
            int num = list2.get(i);
            if (!unionList.contains(num)) {
                unionList.add(num);
            }
        }

        return unionList;
    }
}

运行示例：

Enter five integers for list1: 3 5 45 4 3
Enter five integers for list2: 33 51 5 4 13
The combined list is 3 5 45 4 33 51 13