Add samples for iterator-related extensions (KT-20357)

libraries/stdlib/samples/test/samples/collections/iterators.kt

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package samples.collections
+
+import samples.Sample
+import java.util.*
+
+class Iterators {
+
+    @Sample
+    fun iteratorForEnumeration() {
+        val vector = Vector<String>().apply {
+            add("RED")
+            add("GREEN")
+            add("BLUE")
+        }
+
+        for (e in vector.elements()) {
+            println("The element is $e")
+        }
+    }
+
+    @Sample
+    fun iterator() {
+        val mutableList = mutableListOf(1, 2, 3)
+        val mutableIterator = mutableList.iterator()
+
+        if (mutableIterator.hasNext()) {
+            mutableIterator.next()
+            mutableIterator.remove()
+        }
+
+        for (e in mutableIterator) {
+            println("The element is $e")
+        }
+    }
+
+    @Sample
+    fun withIndexIterator() {
+        val iterator = ('a'..'c').iterator()
+
+        for ((index, value) in iterator.withIndex()) {
+            println("The element at $index is $value")
+        }
+    }
+
+    @Sample
+    fun forEachIterator() {
+        val iterator = (1..3).iterator()
+        if (iterator.hasNext()) {
+            iterator.next()
+        }
+
+        iterator.forEach {
+            println("The element is $it")
+        }
+    }
+}

libraries/stdlib/src/kotlin/collections/Iterators.kt

@@ -5,6 +5,7 @@ package kotlin.collections
 
 /**
  * Creates an [Iterator] for an [Enumeration], allowing to use it in `for` loops.
+ * @sample samples.collections.Iterators.iteratorForEnumeration
  */
 @kotlin.jvm.JvmVersion
 public operator fun <T> java.util.Enumeration<T>.iterator(): Iterator<T> = object : Iterator<T> {
@@ -15,6 +16,7 @@ public operator fun <T> java.util.Enumeration<T>.iterator(): Iterator<T> = objec
 
 /**
  * Returns the given iterator itself. This allows to use an instance of iterator in a `for` loop.
+ * @sample samples.collections.Iterators.iterator
  */
 @kotlin.internal.InlineOnly
 public inline operator fun <T> Iterator<T>.iterator(): Iterator<T> = this
@@ -22,11 +24,13 @@ public inline operator fun <T> Iterator<T>.iterator(): Iterator<T> = this
 /**
  * Returns an [Iterator] wrapping each value produced by this [Iterator] with the [IndexedValue],
  * containing value and it's index.
+ * @sample samples.collections.Iterators.withIndexIterator
  */
 public fun <T> Iterator<T>.withIndex(): Iterator<IndexedValue<T>> = IndexingIterator(this)
 
 /**
  * Performs the given [operation] on each element of this [Iterator].
+ * @sample samples.collections.Iterators.forEachIterator
  */
 public inline fun <T> Iterator<T>.forEach(operation: (T) -> Unit) : Unit {
     for (element in this) operation(element)