working filterIsInstance() helper method for filtering on a sub type

libraries/stdlib/src/Iterators.kt

@@ -5,14 +5,14 @@ import kotlin.support.AbstractIterator
 import java.util.*
 import java.util.Iterator
 
-/** Filters the iterator for all elements of a certain kind */
-inline fun <T, R: T> java.util.Iterator<T>.filterIs(): Iterator<R> = FilterIsIterator<T,R>(this)
+/** Filters the iterator for all elements of a certain sub class */
+inline fun <T, R: T> java.util.Iterator<T>.filterIsInstance(klass: Class<R>): Iterator<R> = FilterIsIterator<T,R>(this, klass)
 
-private class FilterIsIterator<T, R :T>(val iter: java.util.Iterator<T>) : AbstractIterator<R>() {
+private class FilterIsIterator<T, R :T>(val iter: java.util.Iterator<T>, val klass: Class<R>) : AbstractIterator<R>() {
     override fun computeNext(): R? {
         while (iter.hasNext()) {
             val next = iter.next()
-            if (next is R) {
+            if (klass.isInstance(next)) {
                 return next as R
             }
         }

libraries/stdlib/src/dom/Dom.kt

@@ -225,10 +225,10 @@ protected class PreviousSiblingIterator(var node: Node) : AbstractIterator<Node>
 }
 
 /** Returns an [[Iterator]] of all the next [[Element]] siblings */
-fun Node.nextElements(): Iterator<Element> = nextSiblings().filterIs<Node, Element>()
+fun Node.nextElements(): Iterator<Element> = nextSiblings().filterIsInstance<Node, Element>(javaClass<Element>())
 
 /** Returns an [[Iterator]] of all the previous [[Element]] siblings */
-fun Node.previousElements(): Iterator<Element> = previousSiblings().filterIs<Node, Element>()
+fun Node.previousElements(): Iterator<Element> = previousSiblings().filterIsInstance<Node, Element>(javaClass<Element>())
 
 /** Returns the attribute value or empty string if its not present */
 inline fun Element.attribute(name: String): String {

libraries/stdlib/test/dom/DomBuilderTest.kt

@@ -61,7 +61,9 @@ class DomBuilderTest() : TestCase() {
         assertEquals(1, doc["#id3"].size())
 
         val root = doc.rootElement
-        if (root != null) {
+        if (root == null) {
+            fail("No root!")
+        } else {
             assertTrue {
                 root.hasClass("bar")
             }
@@ -82,10 +84,13 @@ class DomBuilderTest() : TestCase() {
             assertEquals(1, root["#id1"].size())
             assertEquals(1, root["#id2"].size())
             assertEquals(1, root["#id3"].size())
-        } else {
-            fail("No root!")
-        }
 
+            // iterating through next element siblings
+            for (e in root.nextElements()) {
+                println("found element: $e")
+            }
+
+        }
         val grandChild = doc["grandChild"].first
         if (grandChild != null) {
             println("got element ${grandChild.toXmlString()} with text '${grandChild.text}`")
@@ -119,5 +124,6 @@ class DomBuilderTest() : TestCase() {
         val xml = nodesToXmlString(children)
         println("root element has children: ${xml}")
         assertEquals(1, children.size())
+
     }
 }