CODEWITHSUNDEEP
java
user2640331
user2640331

Reputation: 51

Creating a list that is iterable

I'm trying to make a list that is iterable and I'm stuck in the iterator part

this is my code

import java.util.Iterator;

public class MappableList<T> implements Iterable<T> {

T list[];

public MappableList(T arg1, T arg2, T arg3, T arg4) {
    list = (T[]) new Object[4];

    list[0] = arg1;
    list[1] = arg2;
    list[2] = arg3;
    list[3] = arg4;

}

void printList() {
    for (int i = 0; i < 4; i++) {
        System.out.println(list[i]);
    }

}

@Override
public Iterator<T> iterator() {
    Iterator<T> iter = new list.iterator();
    return iter;
}
}

it doesnt work at the part 

Iterator<T> iter = new list.iterator();

any ideas or thoughts?

Thanks

Upvotes: 1

Views: 236

Answers (3)

x4u
x4u

Reputation: 14077

Assuming your array is meant to be always entirely filled with elements, a minimal Iterator implementation could look like this:

@Override public Iterator<T> iterator()
{
    final T[] list = this.list;
    return new Iterator<T>()
    {
        int idx;
        public boolean hasNext() { return idx < list.length; }
        public T       next()    { return list[ idx++ ]; }
        public void    remove()  { throw new UnsupportedOperationException(); }
    };
}

By the way, you should consider to declare the list member as private. Accessing it directly from places with knowledge about a narrower definition for type T (i.e. specialzed subclasses) could lead to ClassCastExceptions at runtime even though the code would compile fine with just a warning for the (T[]) cast you get in the contructor.

Upvotes: 0

A4L
A4L

Reputation: 17595

You have declared list is an array, and as such it has no member iterator() and less an inner class. iterator to make an instance of.

You could implement your iterator index based where hasNext() returns index < actIndex and next() returns list[itIndex] and throws a NoSuchElementException if it was called after hasNext() returned false.

Upvotes: 0

Louis Wasserman
Louis Wasserman

Reputation: 198391

You need to actually reimplement the Iterator interface; there's no such thing as list.iterator().

Upvotes: 2

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