Java:如何合并两个 map 的键？

Question

我在 Java 中工作，并声明了两个映射如下:

private Map<MyCustomClass, Integer> map1, map2;
map1 = new HashMap<MyCustomClass, Integer>();
map2 = new HashMap<MyCustomClass, Integer>();

//adding some key value pair into map1
//adding some key value pair into map2

private ArrayList<MyCustomClass> list = new ArrayList<MyCustomClass>(); 

现在我想在上面声明的 ArrayList 中插入两个映射的键。是否存在任何内置方法，或者我需要编写一些自定义代码？

Answer 1

添加所有内容:

list.addAll(map1.keySet());
list.addAll(map2.keySet());

仅添加唯一键:

Set<MyCustomClass> keys = new HashSet(map1.keySet());
keys.addAll(map2.keySet());

list.addAll(keys);

引用文献: List.addAll(Collection c) ; HashMap.keySet()