src/main/java/com/fishercoder/solutions/_705.java

package com.fishercoder.solutions;

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

public class _705 {
    public static class Solution1 {
        class MyHashSet {
            Map<Integer, Integer> map;

            /**
             * Initialize your data structure here.
             */
            public MyHashSet() {
                map = new HashMap<>();
            }

            public void add(int key) {
                map.put(key, 0);
            }

            public void remove(int key) {
                if (map.containsKey(key)) {
                    map.remove(key);
                }
            }

            /**
             * Returns true if this set contains the specified element
             */
            public boolean contains(int key) {
                return map.containsKey(key);
            }
        }
    }
}