Split an array list in Java

This is probably less memory-efficient — but probably a better solution in general.


ArrayList list = new ArrayList() ;
.
list.put( new String( "Hello" ) ) ;  // or whatever
.
// if list.size() > 900
String [] block = new String [900] ;  // 0-899
String [] rest   = new Stirng [list.size()-900] ;

String [] array = (String [] ) list.toArray() ;

System.arraycopy( array, 0, block, 0, 900 ) ;
System.arraycopy( rest, 900, rest, 0, list.size()-900 ) ;

I would use ArrayList.clone() followed by ArrayList.removeRange() on each of the two lists.

The clone() method makes a shallow copy of the array list, so creates a copy of the list, but does not copy the objects within the list.  [ In other words, the two lists each point to all the same object instances. ]  Use the removeRange() method to remove the first 1000 elements from one list and the post-1000 elements from the other list.  I like this approach because the items contained within the list do not get duplicated in the process.  

However, it would be naive to assume that iteration does not occur.  It just gets pushed from your code into the methods of ArrayList.

ArrayList list = new ArrayList();
list.add(new Long(0));
list.add(new Long(1));
list.add(new Long(2));
list.add(new Long(3));
list.add(new Long(4));
list.add(new Long(5));
            
ArrayList list1 = new ArrayList(list.subList(0, 3));
ArrayList list2 = new ArrayList(list.subList(3, 6));
            
System.out.println(list1);
System.out.println(list2);

this code will print -
[0, 1, 2]
[3, 4, 5]

-wings

The List could be 3000 or 4000 so I need chunks of 900