1 import java.util.ArrayList;
 2 import java.util.Arrays;
 3 import java.util.HashMap;
 4 import java.util.Map;
 5 public class Solution {
 6     //Insert one char from stringstream
 7      ArrayList<Character>list=new ArrayList<Character>();
 8     Map<Character,Integer>map=new HashMap<Character,Integer>();
 9      char c;
10     public void Insert(char ch)
11     { 
12         list.add(ch);
13         if(map.containsKey(ch)){
14         map.put(ch,map.get(ch)+1);
15     }else{
16         map.put(ch,1);
17     }
18     boolean flag=false;
19     for(int i=0;i<list.size();i++){
20         if(map.get(list.get(i))==1){
21             c=list.get(i);
22             flag=true;
23             break;
24         }
25            
26     }
27     if(!flag)
28         c='#';
29     }
30   //return the first appearence once char in current stringstream
31     public char FirstAppearingOnce()
32     {
33        return c;
34     }
35 }