src/java.base/share/classes/java/util/stream/LongStream.java

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2016, 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

@@ -898,10 +898,74 @@
                 iterator,
                 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
     }
 
     /**
+     * Returns a sequential ordered {@code LongStream} produced by iterative
+     * application of a function {@code f} to an initial element {@code seed},
+     * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
+     * {@code f(f(seed))}, etc.  The stream terminates when {@code predicate}
+     * returns false.
+     *
+     * <p>The first element (position {@code 0}) in the {@code LongStream} will be
+     * the provided {@code seed}.  For {@code n > 0}, the element at position
+     * {@code n}, will be the result of applying the function {@code f} to the
+     * element at position {@code n - 1}.
+     *
+     * @param seed the initial element
+     * @param predicate a predicate to apply to elements to determine when the 
+     *          stream must terminate.
+     * @param f a function to be applied to the previous element to produce
+     *          a new element
+     * @return a new sequential {@code LongStream}
+     * @since 9
+     */
+    public static LongStream iterate(long seed, LongPredicate predicate, LongUnaryOperator f) {
+        Objects.requireNonNull(f);
+        Objects.requireNonNull(predicate);
+        Spliterator.OfLong spliterator = new Spliterators.AbstractLongSpliterator(Long.MAX_VALUE, 
+               Spliterator.ORDERED | Spliterator.IMMUTABLE) {
+            long prev;
+            boolean started, finished;
+
+            @Override
+            public boolean tryAdvance(LongConsumer action) {
+                Objects.requireNonNull(action);
+                if (finished)
+                    return false;
+                long t;
+                if (started)
+                    t = f.applyAsLong(prev);
+                else {
+                    t = seed;
+                    started = true;
+                }
+                if (!predicate.test(t)) {
+                    finished = true;
+                    return false;
+                }
+                action.accept(prev = t);
+                return true;
+            }
+
+            @Override
+            public void forEachRemaining(LongConsumer action) {
+                Objects.requireNonNull(action);
+                if (finished)
+                    return;
+                long t = started ? f.applyAsLong(prev) : seed;
+                finished = true;
+                while (predicate.test(t)) {
+                    action.accept(t);
+                    t = f.applyAsLong(t);
+                }
+            }
+        };
+        return StreamSupport.longStream(spliterator, false);
+    }
+
+    /**
      * Returns an infinite sequential unordered stream where each element is
      * generated by the provided {@code LongSupplier}.  This is suitable for
      * generating constant streams, streams of random elements, etc.
      *
      * @param s the {@code LongSupplier} for generated elements