You have created an array that holds five references to player objects, but you haven't created any Player objects for them to reference. So players is a reference to a player object but its value is currently null.
When you create a Java array of some kind of object, what you get is an array of references to objects. All of those references are null. You can't use the objects in the array, because there are no objects in the array. You need to put objects in there first -- i.e.,