Compile Time Error, No idea what is happening ?? Please help me...

@admin, i am getting following compile time error while submitting my code. Please tell me what to do. I am not getting any error in my machine. What should i do ? error: cannot find symbol
h.replace(str.substring(j,j+1), h.get(str.substring(j,j+1))+1);
symbol: method replace(String,int)
location: variable h of type Map<String,Integer>
1 error