hand write hashmap

Hashmap.java

class MyHashMap {
    static class Node {
        public int key;
        public int value;
        public Node prev;
        public Node next;
    }

    static Node first;
    static Node last;

    public MyHashMap() {
    }

    public void put(int key, int value) {
        Node n = new Node();
        n.key = key;
        n.value = value;
        if (first == null) {
            first = n;
            last = n;
        } else {
            Node tmp = first;
            for (; tmp != null; tmp = tmp.next) {
                if (tmp.key == key) {
                    tmp.value = value;
                    return;
                }
            }
            // append to last
            last.next = n;
            // System.out.println(String.format("%v/%v/%v", first, n, last));
            n.prev = last;
            last = n;
        }
    }

    public int get(int key) {
        if (first == null) {
            return -1;
        }
        Node n = first;
        for (; n != null; n = n.next) {
            // System.out.println(String.format("n %d/%d, target key is %d", n.key, n.value,
            // key));
            if (n.key == key) {
                // System.out.println(String.format("found n %d/%d, target key is %d", n.key,
                // n.value, key));
                return n.value;
            }
        }
        return -1;
    }

    public void remove(int key) {
        Node n = first;
        for (; n != null; n = n.next) {
            if (n.key == key) {
                n.prev.next = n.next;
                return;
            }
        }
    }
}

/**
 * Your MyHashMap object will be instantiated and called as such:
 * MyHashMap obj = new MyHashMap();
 * obj.put(key,value);
 * int param_2 = obj.get(key);
 * obj.remove(key);
 */