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Checking whether an object is an instance of List <Object>

I have Objectone that sometimes contains List<Object>. I want to test it with instanceof, and if so, add some elements to it.

void add(Object toAdd) {
    Object obj = getValue();
    if (obj instanceof List<?>) {
        List<?> list = obj;
        if (list instanceof List<Object>) {    // Error
            ((List<Object>) list).add(toAdd);
        } else {
            List<Object> newList = new ArrayList<Object>(list);
            newList.add(toAdd);
            setValue(newList);
        }
        return;
    }
    throw new SomeException();
}

And he says that I cannot check if it instanceof List<Object>is because java does not care and erases the type in <>. Does this mean that I have to create a new ArrayList every time? Or is there a way to check this, for example. with reflection?

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1 answer

, . , - , -.

void add(Object toAdd) {
    Object obj = getObject();
    if (obj instanceof List<?>) {
        ((List<Object>)obj).add(toAdd);
        return;
    }
    throw new SomeException();
}

UPDATE

, , - , , , :

List<String> x1 = new ArrayList<String>();
Object c3 = x1;
x1.add("asdsad");
Integer y2 = new Integer(5);
if (c3 instanceof List<?>){
     ((List<Object>)c3).add((Object)y2);
}

for (Object i : (List<Object>)c3){
    if (i instanceof String){
        System.out.println("String: " + (String)i);
    }
    if (i instanceof Integer){
        System.out.println("Integer: "+ (Integer)i);
    }
}
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