Can I iterate through a NodeList using for-each in Java?

Question

I want to iterate through a NodeList using a for-each loop in Java. I have it working with a for loop and a do-while loop but not for-each.

Node         


        

Answer 1

I know it is late to the party, but...
Since Java-8 you can write @RayHulha's solution even more concisely by using lambda expression (for creating a new Iterable) and default method (for Iterator.remove):

public static Iterable<Node> iterable(final NodeList nodeList) {
    return () -> new Iterator<Node>() {

        private int index = 0;

        @Override
        public boolean hasNext() {
            return index < nodeList.getLength();
        }

        @Override
        public Node next() {
            if (!hasNext())
                throw new NoSuchElementException();
            return nodeList.item(index++); 
        }
    };
}

and then use it like this:

NodeList nodeList = ...;
for (Node node : iterable(nodeList)) {
    // ....
}

or equivalently like this:

NodeList nodeList = ...;
iterable(nodeList).forEach(node -> {
    // ....
});

Answer 2

The validated solution is very useful, but here I share an improved solution based on the valid one, this helps you iterate as well, but easy to use, and secure:

public class XMLHelper {
    private XMLHelper() { }

    public static List<Node> getChildNodes(NodeList l) {
        List<Node> children = Collections.<Node>emptyList();
        if (l != null && l.getLength() > 0) {
            if (l.item(0) != null && l.item(0).hasChildNodes()) {
                children = new NodeListWrapper(l.item(0).getChildNodes());
            }
        }
        return children;
    }

    public static List<Node> getChildNodes(Node n) {
        List<Node> children = Collections.<Node>emptyList();
        if (n != null && n.hasChildNodes()) {
            NodeList l = n.getChildNodes();
            if (l != null && l.getLength() > 0) {
                children = new NodeListWrapper(l);
            }
        }
        return children;
    }

    private static final class NodeListWrapper extends AbstractList<Node> implements RandomAccess {
        private final NodeList list;
        NodeListWrapper(NodeList l) {
            list = l;
        }
        public Node get(int index) {
            return list.item(index);
        }
        public int size() {
            return list.getLength();
        }
    }

}

Usage:

 for (Node inner : XMLHelper.getChildNodes(node)) { ... }

Thanks @Holger.

Answer 3

There are ready to use or copypaste iterator implementations in org.apache.commons.collections4.iterators.NodeListIterator and com.sun.xml.internal.ws.util.xml.NodeListIterator.

Answer 4

public static Iterable<Node> iterable(final NodeList n) {
  return new Iterable<Node>() {

    @Override
    public Iterator<Node> iterator() {

      return new Iterator<Node>() {

        int index = 0;

        @Override
        public boolean hasNext() {
          return index < n.getLength();
        }

        @Override
        public Node next() {
          if (hasNext()) {
            return n.item(index++);
          } else {
            throw new NoSuchElementException();
          }  
        }

        @Override
        public void remove() {
          throw new UnsupportedOperationException();
        }
      };
    }
  };
}

Answer 5

Adding the happy little kotlin version for sience:

fun NodeList.forEach(action: (Node) -> Unit) {
    (0 until this.length)
            .asSequence()
            .map { this.item(it) }
            .forEach { action(it) }
}

One can then use it with nodeList.forEach { do_something_awesome() }

Answer 6

As NodeList is just an interface, you could create a class which would implement both NodeList and Iterable, in order to iterate through it.