I have an ArrayList with Object[]'s and I need to convert the ArrayList into an Object[][] array in order to put the data in a JTable. How can I do this?
I have tried:
(Object[][]) arraylist.toArray();
but that gave:
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [[Ljava.lang.Object;
You can use toArray, like this:
Object[][] array2d = (Object[][])arraylist.toArray(new Object[arraylist.size()][]);
This is a non-generic version; generic toArray(T[] a) lets you avoid the cast.
Object[] instead of an Object[][] according to Netbeans
Try this, an explicit solution that takes into account arrays with variable lengths:
ArrayList<Object[]> input = new ArrayList<>();
Object[][] output = new Object[input.size()][];
for (int i = 0; i < input.size(); i++) {
Object[] array = input.get(i);
output[i] = new Object[array.length];
System.arraycopy(array, 0, output[i], 0, array.length);
}
for loop, you can use System.arraycopy(array, 0, output[i], 0, array.length);
List<Object[]> list = new ArrayList();
list.add(new Object[]{1,2,3});
Object[][] objArray = new Object[list.size()][];
for (int i=0;i<objArray.length;i++)
objArray[i] = list.get(i).clone();
