Understanding Decision Stump in Adaboost
I wonder if you what decision stump is. 

Decision stump is simply a decision tree with only one node. It is usually considered as the weak classifier in boosting algorithms since due to its simplicity it will not overfit.

In your question it is not clear what is even 1 .. 3. Anyhow, the classifiers can be : decision stump1, decision stump2 and decision stump3.