将HashSet放入HashMap中 [英] Putting HashSet inside a HashMap

问题描述

是否有任何方法可以通过将哈希集添加到HashMap中，然后在不更改先前放置在hashMap中的HashSet的情况下更改HashSet的方式进行重用?

Is there any way to reuse a hash set by adding it to the HashMap, then later changing the HashSet without it changing the previous HashSet that was placed into the hashMap?

public static void hash() {
    HashMap<Integer, HashSet<Integer>> hset = new HashMap<Integer, HashSet<Integer>>(
    HashSet<Integer> list = new HashSet<Integer>();

    list.add(1);
    list.add(2);
    list.add(3);
    list.add(4);
    hset.put(1,list);

    System.out.println(hset.get(1));
    // the console prints "[1, 2, 3, 4]"
    list.clear();
    
    
    System.out.println(hset.get(1));
    // the console prints "[]"
    
}

我想获取HashSet的用户输入，将其存储在HashMap中，然后清除要由用户再次使用的HashSet.但是我需要使用相同的HashSet，因为会有一个循环.

I want to take user inputs for the HashSet, store them in the HashMap, then clear the HashSet to be used again by the user. But I need to use the same HashSet as there will be a loop.

推荐答案

放入一个新的 HashSet ，该列表由 list 的元素组成.

Put a new HashSet consisting of the elements of list.

hset.put(1, new HashSet<>(list));

演示:

import java.util.HashMap;
import java.util.HashSet;

public class Main {
    public static void main(String[] args) {
        HashMap<Integer, HashSet<Integer>> hset = new HashMap<>();
        HashSet<Integer> list = new HashSet<>();

        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        hset.put(1, new HashSet<>(list));

        System.out.println(hset.get(1));
        // the console prints "[1, 2, 3, 4]"
        list.clear();

        System.out.println(hset.get(1));
        // the console prints "[1, 2, 3, 4]"
    }
}

在旁注中，您只需要在右侧<> 即可，即可以代替 new HashMap< Integer，HashSet< Integer>> 只需编写 new HashMap<> .

On a side note, you need just <> on the right side i.e. instead of new HashMap<Integer, HashSet<Integer>>, you can simply write new HashMap<>.

这篇关于将HashSet放入HashMap中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！