CODEWITHSUNDEEP
javaarraysarraylist
gadon
gadon

Reputation: 353

Get exception while using System.arraycopy for copy to ArrayList, gets: ArrayStoreException: null

I have some trouble while trying to copy two arrays. Consider following simple code: 

    ArrayList<Integer> t1 = new ArrayList<Integer>();
    Integer i1 = new Integer(1);
    Integer i2 = new Integer(2);
    t1.add(i1);
    t1.add(i2);

    ArrayList<Integer> t2 = new ArrayList<Integer>();
    System.arraycopy(t1, 0, t2, 0, t1.size());

Console shows: java.lang.ArrayStoreException: null . What can be wrong in this code, or how can I do it in different way. Sorry about may be easy question but I'm stuck on this for some hours and can't fix it.

Upvotes: 5

Views: 5372

Answers (4)

el.nicko
el.nicko

Reputation: 473

In case anybody wants to add just a portion of the second ArrayList, one might do it like this:

ArrayList<Integer> t1 = new ArrayList<Integer>();
Integer i1 = new Integer(1);
Integer i2 = new Integer(2);
Integer i3 = new Integer(3);
t1.add(i1);
t1.add(i2);
t1.add(i3);

ArrayList<Integer> t2 = new ArrayList<Integer>();

/*
 * will add only last two integers
 * as it creates a sub list from index 1 (incl.)
 * to index 3 (excl.)
 */
t2.addAll(t1.subList(1, 3));

System.out.println(t2.size()); // prints 2
System.out.println(t2.get(0)); // prints 2
System.out.println(t2.get(1)); // prints 3

Upvotes: 1

Javier
Javier

Reputation: 12398

easier:

ArrayList<Integer> t2 = new ArrayList<Integer>(t1);

or if the t2 has already been created

t2.clear();
t2.addAll(t1);

Upvotes: 0

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41220

You need Collections#copy

Collections.copy(t1,t2);

It will copies all of the elements from t1 list into t2.

Upvotes: 3

Eric Galluzzo
Eric Galluzzo

Reputation: 3241

System.arraycopy expects arrays (e.g. Integer[]) as the array parameters, not ArrayLists.

If you wish to make a copy of a list like this, just do the following:

List<Integer> t2 = new ArrayList<Integer>(t1);

Upvotes: 12

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