When to use generic methods and when to use wild-card?

Question

I am reading about generic methods from OracleDocGenericMethod. I am pretty confused about the comparison when it says when to use wild-card and when to use generic methods.

Answer 1

One other difference which is not listed here.

static  void fromArrayToCollection(T[] a, Collection c) {
    for (T o : a) {
        c.add(o); // correct
    }
}

But the following will result in compile time error.

static  void fromArrayToCollection(T[] a, Collection c) {
    for (T o : a) {
        c.add(o); // compile time error
    }
}