Java.ArrayList. method remove()

Question

ArrayList have metod remove(int index) and remove(Object o), so

i try run this code: public static void main(String args[]){

    ArrayList<Long>ar=new ArrayList<Long>();

    ar.add(11L);
    ar.add(22L);
    ar.add(33L);

    ar.remove(new Integer(33)); // 1

    byte b =0;
    ar.remove(b);  //2

    for(Iterator i=ar.iterator(); i.hasNext();)
    {
        System.out.println(i.next());

    }

}

in result i have:

22
33

My question:

in line 1 parameter Integer - why we not have exception?
line 2 - paramenet byte - its not int and not Object, why not Exception again?

so, if i correctly understand for line 1 we have this situation: in our list we have Long, so when we try run remove method we have this: If(Integer.equals(Long)) returns false, our list not modified. — user471011
and next. byte -> int. its correct. but if i do this: long b =4654654654654654654L; long to int - imposible. — user471011

Bozho Bozho · Accepted Answer · 2010-12-07T23:02:21

The remove(..) method is not generic. It accepts any object and does not check its class. The condition it should meed in order for an element to be remove is the equals(..) method to return true when compared to an element in the collection. The element 33 is not removed, because Long.equals(..) returns false if the other object is not instanceof Long
the byte is interpreted as the index.

Java.ArrayList. method remove()

6 Answers