List class's toArray in Java- Why can't I convert a list of “Integer” to an “Integer” array?

Question

I defined List stack = new ArrayList();

When I\'m trying to convert it to an array in the following way:

Answer 1

The way to do it is this:

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

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For the record, the reason that your code doesn't compile is not just type erasure. The problem is that List<T>.toArray() returns an Object[] and it has done this before generics were introduced.

Answer 2

Because of type erasure, the ArrayList does not know its generic type at runtime, so it can only give you the most general Object[]. You need to use the other toArray method which allows you to specify the type of the array that you want.

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

Answer 3

Do this instead:

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

We need to pass the "seed" array as an argument to the toArray method.