/*
    This is a hashtable implementation for javascript. support all the functions of hashtable which can be used to
    perform key-value mapping of data
*/

 function Hashtable(){
                    this.clear = hashtable_clear;
                    this.containsKey = hashtable_containsKey;
                    this.containsValue = hashtable_containsValue;
                    this.get = hashtable_get;
                    this.isEmpty = hashtable_isEmpty;
                    this.keys = hashtable_keys;
                    this.put = hashtable_put;
                    this.remove = hashtable_remove;
                    this.size = hashtable_size;
                    this.toString = hashtable_toString;
                    this.values = hashtable_values;
                    this.hashtable = new Array();
                }
                /*=======Private methods for internal use only========*/

                function hashtable_clear(){
                    this.hashtable = new Array();
                }

                function hashtable_containsKey(key){
                    var exists = false;
                    for (var i in this.hashtable) {
                        if (i == key && this.hashtable[i] != null) {
                            exists = true;
                            break;
                        }
                    }
                    return exists;
                }

                function hashtable_containsValue(value){
                    var contains = false;
                    if (value != null) {
                        for (var i in this.hashtable) {
                            if (this.hashtable[i] == value) {
                                contains = true;
                                break;
                            }
                        }
                    }
                    return contains;
                }

                function hashtable_get(key){
                    return this.hashtable[key];
                }

                function hashtable_isEmpty(){
                    return (this.size == 0) ? true : false;
                }

                function hashtable_keys(){
                    var keys = new Array();
                    for (var i in this.hashtable) {
                        if (this.hashtable[i] != null)
                            keys.push(i);
                    }
                    return keys;
                }

                function hashtable_put(key, value){
                    if (key == null || value == null) {
                        throw "NullPointerException {" + key + "},{" + value + "}";
                    }else{
                        this.hashtable[key] = value;
                    }
                }

                function hashtable_remove(key){
                    var rtn = this.hashtable[key];
                    this.hashtable[key] = null;
                    return rtn;
                }

                function hashtable_size(){
                    var size = 0;
                    for (var i in this.hashtable) {
                        if (this.hashtable[i] != null)
                            size ++;
                    }
                    return size;
                }

                function hashtable_toString(){
                    var result = "";
                    for (var i in this.hashtable)
                    {
                        if (this.hashtable[i] != null)
                            result += "{" + i + "},{" + this.hashtable[i] + "}\n";
                    }
                    return result;
                }

                function hashtable_values(){
                    var values = new Array();
                    for (var i in this.hashtable) {
                        if (this.hashtable[i] != null)
                            values.push(this.hashtable[i]);
                    }
                    return values;
                }