Error while compilation of "Mapped Strings" code

The following code is running fine and giving correct outputs in Netbeans IDE. But on CB platform, following error is shown while compiling…
Note: Main.java uses unchecked or unsafe operations.

Note: Recompile with -Xlint:unchecked for details.

import java.util.*;
public class MappedStrings
{
public static void mapped(String str,String temp,HashMap<String,Character> map) throws Exception
{
if(str.length()==0)
{
System.out.println(temp);
return;
}
mapped(str.substring(1),temp+map.get(str.charAt(0)+""),map);
if(str.length()!=1)
{
String s=str.charAt(0)+""+str.charAt(1)+"";
if(map.containsKey(s))
mapped(str.substring(2),temp+map.get(s),map);
}
}

public static void main(String[] args) throws Exception
{
    Scanner sc=new Scanner(System.in);
    int num=sc.nextInt();
    String str=num+"";
    String letters="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    ArrayList<String> list=new ArrayList<>();
    HashMap<String,Character> map=new HashMap();
    for(int i=1;i<=26;i++)
    {
        map.put(i+"",letters.charAt(i-1));
    }
    mapped(str,"",map);
}

}

@vinay86048,
Your code is correct and should give you a correct answer. https://ide.codingblocks.com/s/228962

Please try to submit again on hackerblocks and if the problem persists kindly write a mail to [email protected] explaining your problem.

I hope I’ve cleared your doubt. I ask you to please rate your experience here
Your feedback is very important. It helps us improve our platform and hence provide you
the learning experience you deserve.

On the off chance, you still have some questions or not find the answers satisfactory, you may reopen
the doubt.