如何将值列表合并到hashmap中的同一个Key？

Question

如何将值列表合并到

key

中的相同

HashMap

？

如果我使用上述逻辑，我将得到以下结果作为输出：

{Adam=[[Subject, ComputerScience], [Subject, ComputerScience]]}

但是我必须像下面的结果一样merge，是否可以将值列表附加到同一个key？

{Adam=[Subject, ComputerScience, Subject, ComputerScience]}

---

示例

public class DemoMap {

    public static void main(String[] args) {
        ArrayList<String> mngrList1 = new ArrayList<>();
        mngrList1.add("Jay");
        mngrList1.add("Aaron");
        
        // Adam is Senior Manager who has the list of managers under him
        HashMap<String, ArrayList<String>> tmeMap = new HashMap<>();
        tmeMap.put("Adam", mngrList1);

        ArrayList<Object> emailContent = new ArrayList<>();
        emailContent.add("Subject");
        emailContent.add("ComputerScience");
        
        HashMap<String, ArrayList<Object>> mngrMap = new HashMap<>();
        mngrMap.put("Jay", emailContent);
        mngrMap.put("Aaron", emailContent);

        // Each manager will have the email content       
        ArrayList<Object> collectionOfManagerContent = new ArrayList<>();
        for (Map.Entry<String,ArrayList<Object>> emailEntry : mngrMap.entrySet()) {
            collectionOfManagerContent.add(emailEntry.getValue());
        }

        // Our goal is to show the manager's content to Senior Project manager      
        HashMap<String, ArrayList<Object>> tmeEmailMap1 = new HashMap<>();
        for (Map.Entry<String,ArrayList<String>> emailEntry : tmeMap.entrySet()) {
            emailEntry.getValue();
            tmeEmailMap1.put(emailEntry.getKey(), collectionOfManagerContent);
        }
        System.out.println(tmeEmailMap1.toString());
    }

}

Answer 1

使用 addAll() 将 ArrayList 的所有元素添加到另一个 ArrayList 中

for (Map.Entry<String,ArrayList<Object>> emailEntry : mngrMap.entrySet()) {
    collectionOfManagerContent.addAll(emailEntry.getValue());
}