Java 如何生成随机响应

当我输入hi时，我试图在Hashset中显示一个响应，但是它显示Hashset中的所有项目。任何帮助都可以。谢谢，下面是我的代码

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

        HashMap<String,HashSet> map = new HashMap<String, HashSet>();
        HashSet<String>hs=new HashSet<String>();

        Random r = new Random();

        hs.add("How are you");
        hs.add("Whats up");
        hs.add("How Have You Been");
        hs.add("Missed Me");
        hs.add("ab");
        hs.add("cd");
        hs.add("Excuse me no no");

        map.put("hi",hs);                

        System.out.println("enter Hi");
        String str=input.next().toLowerCase().trim();

        if(map.containsKey(str)){   
            System.out.println(map.get(str));
        }
    }
}

---

我更改了您的代码并使用了ArrayList而不是HashSet。我不知道在进一步的设计中是否需要哈希集，但使用ArrayList可以通过元素的索引检索元素，而且索引很容易随机获取：

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

    // the HashMap now needs to store Strings and ArrayLists
    HashMap<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
    // the ArrayList replaces your HashSet.
    ArrayList<String> list = new ArrayList<String>();   // I called it list so you we can see the difference :)

    Random r = new Random();

    list.add("How are you");
    list.add("Whats up");
    list.add("How Have You Been");
    list.add("Missed Me");
    list.add("ab");
    list.add("cd");
    list.add("Excuse me no no");

    map.put("hi", list);

    System.out.println("enter Hi");
    String str = input.next().toLowerCase().trim();

    if (map.containsKey(str)) {
        ArrayList<String> tmpList = map.get(str);  // this is just make the step clear, that we now retrieve an ArrayList from the map
        int randomNumber = r.nextInt(tmpList.size()) // a random number between 0 and tmpList.size() 
        System.out.println(tmpList.get(randomNumber)); // get the random response from the list
    }
}

---

这是因为您正在打印map.getstr，这是整个集合。如果我需要单独打印一个，我缺少什么？为什么不使用ArrayList而不是HashSet，然后随机拉出一个字符串：map.getstr.getr.nextInMyArrayList.size。。像这样的？

enter Hi
Hi
How Have You Been