Best way to copy from one array to another

When I run the following code, nothing gets copied - what am I doing wrong?

Also, is this the best/most efficient way to copy data from one array to another?

public class A {
    public static void main(String args[]) {
        int a[] = { 1, 2, 3, 4, 5, 6 };
        int b[] = new int[a.length];

        for (int i = 0; i < a.length; i++) {
            a[i] = b[i];
        }
    }
}