Hello everybody, i'm posting for the first time here to maybe solve a very disturbing problem. I simply can't use an array list I must say that i'm a beginner in spigot. First time i tried to use one, i created it in my main class and created an instance to permit ther classes interact with my list. That was a command who were stocking the first argument (0) , checked if that arg were an online player , and if it was, stocking him into my player array list . Player in that list could use another command. But, it didn't work. When i was trying my first command, i had an internal error, same for the second one So i tried to create a new array list that get a player when he join (player join event) and send a message to the player that just connected to tell him the size of the array list. But, AGAIN, i had no error in eclipse, everything seemed to be okay, and when i connected; i received nothing and seen an internal error. Here are some screen shots of my main class and the listener one.