prevent duplicate items

[Cathy105]

I'm extremely new to Java. I have set up a database using a vector. Everything runs fine. When I select an item from my database, it goes to a table in my program. However, I can select the item a million times and it will show up a million times.

How can I indicate that I have added a duplicate item to the list and keep the user from being able to select the item again? If anyone has any ideas...or can tell me where I can find information.


void cmdRequest_actionPerformed(ActionEvent e) {
System.out.println("hit the add to list button"
DogObject dg = (DogObject)vDog.elementAt(iTrack);
vSelect.addElement(dg);
fillCombo();
}

 

[meadandale]

If you don't want duplicates, use a Set instead of a List/Vector. A Set disallows duplicates.

If you are adding user defined types to a set (e.g. your DogObject) then you will have to implement some additional methods/interfaces such as equals(), Comparable and hashCode (depending on which type of Set implementation you use) in order for this to work.

 

[Cathy105]

Appreciate your help. Unfortunately, I am still quite new to this. I tried using equals earlier today, but don't know what I'm doing. I instatiated 2 new DogObjects and tried comparing them in a For loop and if statement using equals but I could not get it to work. I am unfamiliar with hash tables. Can you recommend a good learning site? If you happen to have an code that uses equals and hash tables together that would also be great.

Happy New Year

 

[meadandale]

Try these:

http://www.javaworld.com/javaworld/jw-01-1999/jw-01-object-p2.html

http://www.javaworld.com/javaqa/2002-06/01-qa-0621-hashtable.html