diff --git a/Basic_Of_Algorithm/src/test/openChatting.java b/Basic_Of_Algorithm/src/test/openChatting.java
new file mode 100644
index 0000000..a68d28c
--- /dev/null
+++ b/Basic_Of_Algorithm/src/test/openChatting.java
@@ -0,0 +1,52 @@
+package test;
+
+import java.util.HashMap;
+import java.util.ArrayList;
+
+public class openChatting {
+	
+	public static void main(String[] args) {
+		
+		String[]record = {"Enter uid1234 Muzi", "Enter uid4567 Prodo","Leave uid1234","Enter uid1234 Prodo","Change uid4567 Ryan"};
+		
+		HashMap<String,String> map = new HashMap<>();
+		
+		ArrayList<String> answerList = new ArrayList<>();
+		
+		for(String str : record) {
+			
+			String []temp = str.split(" ");
+			
+			String action = temp[0];
+			String id = temp[1];
+			if(action.equals("Leave"))continue;
+			String nick = temp[2];
+			
+			map.put(id, nick);
+			
+		}
+		
+		
+		for(String str : record) {
+			
+			String []temp = str.split(" ");
+			
+			String action = temp[0];
+			String id = temp[1];
+			if(action.contains("Change"))continue;
+			String nick = map.get(id);
+			
+			String ans = nick+"님이 " + (action.equals("Enter") ? "들어왔습니다." : "나갔습니다."); 
+			
+			answerList.add(ans);
+		}
+		
+		String[]answer = new String[answerList.size()];
+		
+		for(int i=0;i<answer.length;i++)answer[i] = answerList.get(i);
+		
+		for(String str : answer) System.out.println(str);
+		
+	}
+
+}