public interface SymbolTable<Key, Value> {
    
    void          put(Key key, Value value);  // inserts a key-value pair into the table
    
    boolean       contains(Key key);          // returns true if the table contains the specified key
    
    Value         get(Key key);               // returns the value paired with given key
    
    void          delete(Key key);            // removes the given key (and its associated value)
                                              // from the table
    
    boolean       isEmpty();                  // returns true if the table is empty
    
    int           size();                     // returns the number of key-value pairs in the table
    
    Iterable<Key> keys();                     // returns an Iterable collection of all keys in the table
}