Accessing Value From A Separate Hash Table

I am implementing the hash join algorithm for a project with a hard coded hash function. I've hashed the first relation and I've hashed the second relation. The problem is when hashing the second relation I only know how to add the tuple from the second relation into a third relation and not also access the first relation tuple at that time

The "hashtable" structure contains the hashcode of my key as well as the tuple stored in a string. This code below is taking place in the hashing of the second table, my function determines that both these tuples share the same hash code based on the first element in the tuple (element 0) so I add the tuple from my second relation to the qRelation but I also want to add the tuple from the hashtable at that point and I don't know how to access that string

if(hashtable.containsKey(tuple/*(RELATIONA)*/.get(0).hashCode()))
{
//Add the tuple from relation A into qRelation wich matches the
//above condition
qRelation.addAll(tuple/*(RELATIONB)*/);
}