Java Iterator.hasNext() 始终为真

Question

I've already checked other questions like this one but it doesn't seem that I always create a new iterator which checks always the same object.

This is the code

        Iterator<Map.Entry<Node, Float>> it = graph.nodeNeighboursIterator(e); 
        System.out.println("extracted node "+ e.getLabel() + " number of neighbours "+ e.sizeNeighbours());
        while(it.hasNext()) {
            System.out.print(i + " " + e.getLabel() + " " + it +"-");
            i++;
        }

the method graph.nodeNeighboursIterator does this

public Iterator<Map.Entry<Node, Float>> nodeNeighboursIterator(Node n) {
    return this.graph_weighted.get(n).entrySet().iterator();
}

the System.out.println("extracted node "+ e.getLabel() + " number of neighbours "+ e.sizeNeighbours()); prints the right number of neighbours but still the loop doesn't end his cycle, what do you think about it?

Answer 1

it.hasNext() checks if there is more data to be returned. This does not consume the data (in other words, does not iterate over the data). This operation is idempotent .

This is the reason why your loop never ends.

You need to actually consume the data by calling it.next() . it.hasNext() returns false if there are no more elements to return.

Answer 2

You need revise your code to like below

while(it.hasNext()) {
    it.next();
}