Either:

Foo[] array = list.toArray(new Foo[0]);

or:

Foo[] array = new Foo[list.size()];
list.toArray(array); // fill the array

Note that this works only for arrays of reference types. For arrays of primitive types, use the traditional way:

List<Integer> list = ...;
int[] array = new int[list.size()];
for(int i = 0; i < list.size(); i++) array[i] = list.get(i);

Update:

It is recommended now to use list.toArray(new Foo[0]);, not list.toArray(new Foo[list.size()]);.

From JetBrains Intellij Idea inspection:

There are two styles to convert a collection to an array: either using a pre-sized array (like c.toArray(new String[c.size()])) or using an empty array (like c.toArray(new String[0]).

In older Java versions using pre-sized array was recommended, as the reflection call which is necessary to create an array of proper size was quite slow. However since late updates of OpenJDK 6 this call was intrinsified, making the performance of the empty array version the same and sometimes even better, compared to the pre-sized version. Also passing pre-sized array is dangerous for a concurrent or synchronized collection as a data race is possible between the size and toArray call which may result in extra nulls at the end of the array, if the collection was concurrently shrunk during the operation.

This inspection allows to follow the uniform style: either using an empty array (which is recommended in modern Java) or using a pre-sized array (which might be faster in older Java versions or non-HotSpot based JVMs).

If you look at the implementation of toArray(T[] a) of ArrayList<E> class, it is like:

public <T> T[] toArray(T[] a) {
    if (a.length < size)
        // Make a new array of a's runtime type, but my contents:
        return (T[]) Arrays.copyOf(elementData, size, a.getClass());
    System.arraycopy(elementData, 0, a, 0, size);
    if (a.length > size)
        a[size] = null;
    return a;
}

Problem with this method is that you need to pass array of the same generic type. Now consider if this method do not take any argument then the implementation would be something similar to:

public <T> T[] toArray() {
    T[] t = new T[size]; // compilation error
    return Arrays.copyOf(elementData, size, t.getClass());
}

But the problem here is that you can not create generic arrays in Java because compiler does not know exactly what T represents. In other words creation of array of a non-reifiable type (JLS §4.7) is not allowed in Java.

Another important quote from Array Store Exception (JLS §10.5):

If the component type of an array were not reifiable (§4.7), the Java Virtual Machine could not perform the store check described in the preceding paragraph. This is why an array creation expression with a non-reifiable element type is forbidden (§15.10.1).

That is why Java has provided overloaded version toArray(T[] a).

I will override the toArray() method to tell it that it will return an array of E.

So instead of overriding toArray(), you should use toArray(T[] a).

Cannot Create Instances of Type Parameters from Java Doc might also be interesting for you.