add multiset size and isempty methods

Author: joney000

Algorithms/Multiset.java

@@ -6,24 +6,34 @@
 */
 class MultiSet<K> {
 	private HashMap<K, Integer> multiSet = new HashMap<K, Integer>();
-
+	private int size;
 	int get(K key){
 		return multiSet.getOrDefault(key, 0);
 	}
 
 	void add(K key){
+		size++;
 		multiSet.put(key, get(key)+ 1);
 	}
 
 	void remove(K key){
 		int freq = get(key);
+		size--;
 		if(freq == 1){
 			multiSet.remove(key);
 		}else{
 			multiSet.put(key, freq - 1);
 		}
 	}
-  
+	
+	public int size(){
+		return size;
+	}
+
+	public boolean isEmpty(){
+		return size == 0;
+	}
+	
 	@Override
 	public String toString(){
 		return multiSet.toString();