从列表中删除整数

Question

How can I propperly check to see if a List has a defined Integer?

private List<Integer> itemsToDrop = new ArrayList<Integer>();
private int lastRateAdded, lastDropAdded;


if(itemsToDrop.contains(lastDropAdded))
{
      itemsToDrop.remove(lastDropAdded);

}
itemsToDrop.add(DropConfig.itemDrops[npc][1]);
lastRateAdded = itemRate;
lastDropAdded = DropConfig.itemDrops[npc][1];

However, this is throwing the following error

java.lang.IndexOutOfBoundsException: Index: 526, Size: 1

SO, I need to figure out how to properly check to see if an Integer is stored in the List or not

Answer 1

List<Integer> list = new ArrayList<Integer>(Arrays.asList(5, 10, 42));
if (list.contains(10)) {
    list.remove(10); // IOOBE
}

The problem with the above code is that you're actually not calling List#remove(Object) but List#remove(int) , which removes the element at given index (and there's no element at index 10).

Use instead:

List<Integer> list = new ArrayList<Integer>(Arrays.asList(5, 10, 42));
if (list.contains(10)) {
    list.remove((Integer) 10);
}

That way, you force the compiler to use the List#remove(Object) method.

Answer 2

Supposing you have a list

private List<Integer> itemsToDrop = new ArrayList<Integer>();

To answer your questions:

A : To check if an integer belongs to a list of integers, you can use .contains()

itemsToDrop.contains(item)

, where item is an integer. This will return true or false .

B : To add

itemsToDrop.add(item)

C : To remove

itemsToDrop.remove(item)

Edit: Just to be clear, the initial post contained 3 questions which I answered