added mediator sample

mediator/src/main/java/com/iluwatar/PartyImpl.java

@@ -0,0 +1,37 @@
+package com.iluwatar;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class PartyImpl implements Party {
+
+	private List<PartyMember> members;
+	
+	public PartyImpl() {
+		members = new ArrayList<>();
+	}
+	
+	@Override
+	public void act(PartyMember actor, Action action) {
+		for (PartyMember member: members) {
+			if (member != actor) {
+				member.partyAction(action);
+			}
+		}
+	}
+
+	@Override
+	public void addMember(PartyMember member) {
+		members.add(member);
+		member.joinedParty(this);
+	}
+	
+	// somebody hunts for food, call for dinner
+	
+	// somebody spots enemy, alert everybody
+	
+	// somebody finds gold, deal the gold with everybody
+	
+	// somebody tells a tale, call everybody to listen
+	
+}