How can I work out these questions?? Would really appreciate your help. things like looking for things in the Hashmap.

• isRally - takes a String containing a rally code as a parameter and returns true if it represents a rally object stored in the allRallies collection, and false otherwise.
• findRally - takes one String parameter containing the rally code and returns the corresponding Rally object, or null if the rally is not in allRallies.
• findRider - takes one int parameter representing the rider ID and returns the corresponding Rider, or null if the rider is not in allRiders.

private HashMap<String, Rally> allRallies = new HashMap<String, Rally>();
    private ArrayList<Rider> Allriders = new ArrayList<Rider>();
    private ArrayList<Rally> allvenues = new ArrayList<Rally>();

    public Branch()
    {

    }
    public boolean isRally(Rally keys)
    {
//                 for(String keys : AllRallies.getCode())
//         if(into.grtCount() <= 0)
//            {
//                 return true     ;             
//         }
//         return false;
    }