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[10000];

    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 -1;
        }
        ListNode node = find(nodes[i], key);
        return node == null ? -1 : 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;
        }
    }
}