I am having trouble deciding how to use java datastructures. For example, I have to pull three fields from a table. The first field has duplicates but it needs to be the key field for the other two fields. The first field is the name of a database table, and the second and third are the column names of the table, and the data types of the table. Therefore, I need to make a hashmap that will accept duplicate keys?? Or is there some better way to do this. I wish I had a better handle on when to use certain data structures??