Design HashMap

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

• put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
• get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.

Example:

MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);          
hashMap.put(2, 2);        
hashMap.get(1);            // returns 1
hashMap.get(3);            // returns -1 (not found)
hashMap.put(2, 1);          // update the existing value
hashMap.get(2);            // returns 1
hashMap.remove(2);          // remove the mapping for 2
hashMap.get(2);            // returns -1 (not found) 

 class MyHashMap {
     final ListNode[] nodes = new ListNode[];

     public void put(int key, int value) {
         int i = idx(key);
         ListNode first = nodes[i];
         ListNode newNode = new ListNode(key, value);
         if (first == null) {
             nodes[i] = newNode;
         } else {
             ListNode sameNode = find(nodes[i], key);
             if (sameNode == null) {
                 newNode.next = first;
                 nodes[i] = newNode;
             } else {
                 sameNode.val = value;
             }
         }
     }

     public int get(int key) {
         int i = idx(key);
         if (nodes[i] == null) {
             return -;
         }
         ListNode node = find(nodes[i], key);
         return node == null ? - : node.val;
     }

     public void remove(int key) {
         int i = idx(key);
         if (nodes[i] == null) {
             return;
         }
         ListNode current = nodes[i];
         ListNode previous = null;
         while (current != null) {
             if (current.key == key) {
                 if (previous != null) {
                     previous.next = current.next;
                 } else {
                     nodes[i] = current.next;
                 }
                 break;
             } else {
                 previous = current;
                 current = current.next;
             }
         }
     }

     int idx(int key) {
         return Integer.hashCode(key) % nodes.length;
     }

     ListNode find(ListNode node, int key) {
         while (node != null) {
             if (node.key == key) {
                 return node;
             }
             node = node.next;
         }
         return null;
     }

     class ListNode {
         int key, val;
         ListNode next;

         ListNode(int key, int val) {
             this.key = key;
             this.val = val;
         }
     }
 }