You are adding the same ArrayState object every time. You should create a new ArrayState object every time in the while loop to avoid it getting changed every time. This is because by default objects are always passed by reference in Java. Try doing this:

ArrayList arrayListIdle = new ArrayList();


while(rs.next){

    state = new State();
    List<State> arrayState = new ArrayList<State>();

    state.updateStateArray(arrayState);//This function mods the elements of (arrayState);//This 
    state.setArrayStates(arrayState);//add a list of arrayState to the object state
    arrayListIdle.addAll(state);

}

Arrays.asList returns a fixed sized list backed by an array, and you can't add elements to it.

You can create a modifiable list to make addAll work :

List<String> supportedTypes = new ArrayList<String>(Arrays.asList("6500", "7600", "8700"));

No copy of the objects or their data are made; their references are simply added to the list object.

Arrays.asList(coins) gives you a brand new list, but its not the usual type of ArrayList. It's a special type of list with a fixed size array underneath, which means you can't add or remove elements in it. It's stuck at the original size of coins although you can modify the values in it.

addAll(something) adds the coins to a list you've already got, which can be any kind of List. You can call it on an ArrayList that you've already created, and the number of elements will actually increase.

The thing you pass to addAll can't be an array though, it has to be some kind of Collection, because that's the way addAll is defined. In most cases, the simplest thing to do is to pass it one of the unresizeable lists that you get from Array.asList, so something like

myList.addAll(Arrays.asList(coins));