Array Is not subtracting

[vknehra10]

 ResultSet dt=dep_time.executeQuery();
            ArrayList<String> dp_dt=new ArrayList<String>();
            while(dt.next()){
                
                dp_dt.add(dt.getString("dep_time"));
            }
            ResultSet at=arr_time.executeQuery();
            ArrayList<String> al_dt=new ArrayList<String>();
            while(at.next()){
                al_dt.add(at.getString("arr_time"));
                
            }
            
            
            
            
            int d=0;
            int a=0;
            
            String time=null;
            
                String tm[]=dp_dt.toArray(new String[dp_dt.size()]);
                String tm1[]=al_dt.toArray(new String[al_dt.size()]);
                
                String tm2[]=new String[tm.length];
                  
                          for(int j=0;j<tm.length;j++){
                              tm2[j]=tm[j]-tm1[j];         //Its showing a bad operand error..
                          }

[Tolls]

You are trying to subtract two Strings.
You can't do that.

You might need to explain what it is you are trying to do, and what values those Strings contain.
I think I can guess, but it would be best for you to explain it.

[vknehra10]

I am fetching two diferent train time from a table and store into two array list
After that i want to find time taken
So i store into a array and then try to subtract to find time taken...

Thanks

[Norm]

Can the Strings be parsed to date or calendar objects that have methods to do computations?