Iterating over an object of type Iterator<T>

While reading through the Wikipedia article on Generators, I found the following Java implementation to iterate over a generic type Iterator<Integer> produce an infinite sequence of Fibonacci numbers

Iterator<Integer> fibo = new Iterator<Integer>() {
    int a = 1;
    int b = 1;
    int total;

    @Override
    public boolean hasNext() {
        return true;
    }

    @Override
    public Integer next() {
        total = a + b;
        a = b;
        b = total;
        return total;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}
// this could then be used as...
for(int f: fibo) {
    System.out.println("next Fibonacci number is " + f);
    if (someCondition(f)) break;
}

However, the above code does't work when put inside main method of a class. It says 

Can only iterate over an array or an instance of java.lang.Iterable

which is understandable. Does it mean the above example is wrong or incomplete? Am I missing something?

Jon Skeet
people
quotationmark

The code sample on Wikipedia is invalid, but you can easily iterate anyway, just by calling hasNext() and next() explicitly.

// We know that fibo.hasNext() will always return true, but
// in general you don't...
while (fibo.hasNext()) {
    int f = fibo.next();
    System.out.println("next Fibonacci number is " + f);
    if (someCondition(f)) break;
}

people

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