how to add element (or convert an Integer ArrayList) to an Integer Array

Question

here is what i have got

ArrayList<Integer> list = new ArrayList<Integer>();
    Integer a = 50; 
    Integer b = 55;
    Integer c = 98;
    Integer d = 101;
    list.add(a);
    list.add(b);
    list.add(c);
    list.add(d);

now i want to convert this "list" to an Array... e.g.:

Integer[] actual= {50,55,98,101};

anyway how to do it? thanks.

list.toArray(new Integer[0]);

david van brink
– david van brink

2011-11-21 22:11:06 +00:00
Commented Nov 21, 2011 at 22:11 — david van brink
– david van brink, Commented Nov 21, 2011 at 22:11

David Koelle · Accepted Answer · 2011-11-21 22:15:38Z

6

Integer[] array = list.toArray(new Integer[list.size()]);

If you want an int[] array, you'll have to loop over the list and unbox each element explicitly.

See http://download.oracle.com/javase/6/docs/api/java/util/List.html next time you're looking for a method of List.

edited Nov 21, 2011 at 22:15

David Koelle

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answered Nov 21, 2011 at 22:10

JB Nizet

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1 Comment

prunge Over a year ago

Apache Commons Lang's ArrayUtils.toPrimitive methods can help converting between arrays of wrappers and arrays of primitives.

namalfernandolk · Accepted Answer · 2011-11-21 23:29:44Z

1

Sefirosu, for another solution you can do it using Arrays.copyOf() or Arrays.copyOfRange() too.

Integer[] integerArray = Arrays.copyOf(list.toArray(), list.toArray().length, Integer[].class);
Integer[] integerArray = Arrays.copyOfRange(list.toArray(), 0, 4, Integer[].class);

answered Nov 21, 2011 at 23:29

namalfernandolk

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