convert ArrayList<?> to ArrayList<ClassName>

Question

I have generic ArrayList that i am setting up on ArrayAdapter which is also a generic type adapter. Now, i want to convert ArrayList<?> to ArrayList<MyClass>. I have searched alot, but could not figure it out. thanks for the help.

I have these 2 generic type adapters and lists.

private ArrayAdapter<?> GeneralAdapter;
private ArrayList<?> GeneralList;

I am setting this adapter on Listview. and Adding different types of class into list dynamically.like

GeneralList<State>
GeneralList<District>

after setting up this lists i am updating adapter using notifydatasetchanged().

I just need to now convert this GeneralList into ArrayList,ArrayList as i need. I am adding items one at a time and for using it again for other class i clear generalList and then set it up for another class.

Possible duplicate of What is the Collections.checkedList() call for in java? and stackoverflow.com/a/1161243/1527544 — Antoniossss
– Antoniossss, Commented Sep 4, 2018 at 8:14
What exactly do you mean by "convert"? Do you mean "cast"? Do you mean "make a view"? Do you mean "make a new list with only the State elements?" etc — Andy Turner
– Andy Turner, Commented Sep 4, 2018 at 8:34
I want casting type of thing. because what i want is to convert this generic list into appropriate class. — Avi Patel
– Avi Patel, Commented Sep 4, 2018 at 9:08

Jay Dangar · Accepted Answer · 2018-09-04 10:57:15Z

2

using dynamic casting you can achieve this.

If you want List of States from GeneralList, then ->

List<State> states = filter(State.class, GeneralList);

this is your filter function ->

static <T> List<T> filter(Class<T> clazz, List<?> items) {
        return items.stream()
                .filter(clazz::isInstance)
                .map(clazz::cast)
                .collect(Collectors.toList());
}

Source -> dynamic Casting in Java

answered Sep 4, 2018 at 10:57

Jay Dangar

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