Call iterator function with argument Java

Question

I have classes like these below:

public class F implements Iterable<P>
{
    private final List<P> pra = new ArrayList<P>();

    public Iterator<P> iterator() 
    {
        return pra.iterator();
    }
    
    public Iterator<P> iterator(S s)
    {
        return pra.stream().filter(x -> x.s == s).iterator();
    }
}

public class P
{
//some code
}

public enum S
{
//some code
}

And i don't know how to call the iterator function in main by foreach loop.

I mean, when the iterator funcion doesn't have an argument, it is simple:

F f = new F();
for(P x: f)
{
System.out.printf("%s\n", p.toString());
}

but how can I do the same, when the iterator function get an argument?

Ok, I corrected it. But how can I call the iterator function which get an argument by foreach loop? — some nooby questions
– some nooby questions, Commented Oct 24, 2020 at 23:47
You can call it the same way as you did previously, this time adding an argument only. — Aman
– Aman, Commented Oct 24, 2020 at 23:49

khelwood · Accepted Answer · 2020-10-24 23:48:21Z

1

The thing that you need for an enhanced for-loop is not an Iterator, but an Iterable.

If you want to call a method in F with an argument, and get something you can use in an enhanced for-loop, then you need your method to return an Iterable.

public class F {
    private final List<P> pra = new ArrayList<P>();
    
    public Iterable<P> filter(S s) {
        return () -> (pra.stream().filter(x -> x.s==s).iterator());
    }
}

With that, you can use for (P p : f.filter(s)) ...

answered Oct 24, 2020 at 23:48

khelwood

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