在Java中使用方法将集合统一为集合

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

public class ListConcatenation {
    public static void main(String[] args) {
        List<String> list1 = new ArrayList<>();
        list1.add("A");
        list1.add("B");

        List<String> list2 = new ArrayList<>();
        list2.add("C");
        list2.add("D");

        List<String> combinedList = new ArrayList<>(list1);
        combinedList.addAll(list2);

        System.out.println(combinedList); // 输出: [A, B, C, D]
    }
}

import java.util.HashSet;
import java.util.Set;

public class SetConcatenation {
    public static void main(String[] args) {
        Set<Integer> set1 = new HashSet<>();
        set1.add(1);
        set1.add(2);

        Set<Integer> set2 = new HashSet<>();
        set2.add(2);
        set2.add(3);

        Set<Integer> combinedSet = new HashSet<>(set1);
        combinedSet.addAll(set2);

        System.out.println(combinedSet); // 输出: [1, 2, 3] 注意去重
    }
}

import java.util.HashMap;
import java.util.Map;

public class MapConcatenation {
    public static void main(String[] args) {
        Map<String, Integer> map1 = new HashMap<>();
        map1.put("One", 1);
        map1.put("Two", 2);

        Map<String, Integer> map2 = new HashMap<>();
        map2.put("Two", 2); // 重复键，新值会覆盖旧值
        map2.put("Three", 3);

        Map<String, Integer> combinedMap = new HashMap<>(map1);
        combinedMap.putAll(map2);

        System.out.println(combinedMap); // 输出: {One=1, Two=2, Three=3}
    }
}