--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/util/Iterators.java	Wed Jul 01 09:51:48 2015 +0200
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.tools.javac.util;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.function.Function;
+
+/** Utilities for Iterators.
+ *
+ *  <p><b>This is NOT part of any supported API.
+ *  If you write code that depends on this, you do so at your own risk.
+ *  This code and its internal interfaces are subject to change or
+ *  deletion without notice.</b>
+ */
+public class Iterators {
+
+    public static <I, O> Iterator<O> createCompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) {
+        return new CompoundIterator<>(inputs, convertor);
+    }
+
+    private static class CompoundIterator<I, O> implements Iterator<O> {
+
+        private final Iterator<I> inputs;
+        private final Function<I, Iterator<O>> convertor;
+        private Iterator<O> currentIterator;
+
+        public CompoundIterator(Iterable<I> inputs, Function<I, Iterator<O>> convertor) {
+            this.inputs = inputs.iterator();
+            this.convertor = convertor;
+        }
+
+        public boolean hasNext() {
+            while (inputs.hasNext() && (currentIterator == null || !currentIterator.hasNext())) {
+                currentIterator = convertor.apply(inputs.next());
+            }
+            return currentIterator != null && currentIterator.hasNext();
+        }
+
+        public O next() {
+            if (!hasNext())
+                throw new NoSuchElementException();
+
+            return currentIterator.next();
+        }
+
+        public void remove() {
+            throw new UnsupportedOperationException();
+        }
+    }
+}