Design HashSet

class MyHashSet {

    /** Initialize your data structure here. */
    boolean[] arr = new boolean[100];
    public MyHashSet() {
        
    }
    
    public void add(int key) {
        if(key >= arr.length){
            lengthen(key);
        }
        arr[key] = true;
    }
    
    public void remove(int key) {
        if(key < arr.length){
            arr[key] = false;
        }
    }
    
    /** Returns true if this set contains the specified element */
    public boolean contains(int key) {
        if(key < arr.length){
            return arr[key];
        }
        return false;
    }
    public void lengthen(int len){
        arr = Arrays.copyOf(arr, len+2);
    }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */