Generics code remove not working

Question

I wanted to test some stuff out about generics in Java so I wrote a method using generics which takes a list and removes every other element. I wrote this method but it gives an UnsupportedOperationException error. What is the problem here?

    Integer[] strArray = new Integer[] {1, 2, 3, 4, 5}; 
    List<Integer> numbers = Arrays.asList(strArray);
    removeOdd(numbers);
    for (Object o : numbers){
         System.out.println( o );
    }
}
        public static <T> void removeOdd ( List<T> list){
            Iterator<T> itr = list.iterator();
            int i = 0;

                while(itr.hasNext())
                {
                    itr.next();
                    i++;
                    if(i % 2 ==1){
                        itr.remove();
                    }
                }

see http://stackoverflow.com/questions/2965747/ – murat Apr 28 '13 at 22:11 — murat, Apr 28 '13 at 22:11

score 7 · Answer 1 · edited Apr 28 '13 at 23:44

7

Arrays.asList(T...) creates a fixed sized list. You may replace an element, but not add or remove any.

edited Apr 28 '13 at 23:44

Paul Bellora

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answered Apr 28 '13 at 22:11

Ben Schulz

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Reimeus · Accepted Answer · 2013-04-28T22:34:21.697

5

Arrays.asList returns a List whose individual elements may be updated but the addition or removal of elements is not allowed. To create a variable size List, you can use:

List<Integer> numbers = new ArrayList<>(Arrays.asList(strArray));

edited Apr 28 '13 at 22:34

answered Apr 28 '13 at 22:10

Reimeus

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The returned list is backed by the array and may be modified. Calls to `set(int, E)` will successfully replace an element. – Ben Schulz Apr 28 '13 at 22:13
An element may be set but not removed – Reimeus Apr 28 '13 at 22:14
And thus the list is mutable. ;) – Ben Schulz Apr 28 '13 at 22:16

Generics code remove not working

2 Answers2