From ed1d755babdeba49bf3912d2e3788d777293bea2 Mon Sep 17 00:00:00 2001
From: Thomas Neidhart <tn@apache.org>
Date: Sat, 6 Jun 2015 12:16:11 +0000
Subject: [PATCH] Add emptyIfNull method, simplification.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1683900 13f79535-47bb-0310-9956-ffa450edef68
---
 .../commons/collections4/FluentIterable.java  |  9 +++------
 .../commons/collections4/IterableUtils.java   | 19 ++++++++++++++-----
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/main/java/org/apache/commons/collections4/FluentIterable.java b/src/main/java/org/apache/commons/collections4/FluentIterable.java
index 2ae931d9a..84fa47bf4 100644
--- a/src/main/java/org/apache/commons/collections4/FluentIterable.java
+++ b/src/main/java/org/apache/commons/collections4/FluentIterable.java
@@ -449,10 +449,7 @@ public class FluentIterable<E> implements Iterable<E> {
         if (collection == null) {
             throw new NullPointerException("Collection must not be null");
         }
-
-        for (final E element : iterable) {
-            collection.add(element);
-        }
+        CollectionUtils.addAll(collection, iterable);
     }
 
     /**
@@ -468,8 +465,8 @@ public class FluentIterable<E> implements Iterable<E> {
     }
 
     /**
-     * Returns a list containing all elements of this iterable by
-     * traversing its iterator.
+     * Returns a mutable list containing all elements of this iterable
+     * by traversing its iterator.
      * <p>
      * The returned list is guaranteed to be mutable.
      *
diff --git a/src/main/java/org/apache/commons/collections4/IterableUtils.java b/src/main/java/org/apache/commons/collections4/IterableUtils.java
index 91ad37260..9088bd4cb 100644
--- a/src/main/java/org/apache/commons/collections4/IterableUtils.java
+++ b/src/main/java/org/apache/commons/collections4/IterableUtils.java
@@ -27,7 +27,6 @@ import org.apache.commons.collections4.functors.EqualPredicate;
 import org.apache.commons.collections4.iterators.LazyIteratorChain;
 import org.apache.commons.collections4.iterators.ReverseListIterator;
 import org.apache.commons.collections4.iterators.UniqueFilterIterator;
-import org.apache.commons.collections4.iterators.ZippingIterator;
 
 /**
  * Provides utility methods and decorators for {@link Iterable} instances.
@@ -452,9 +451,7 @@ public class IterableUtils {
         if (iterable instanceof UnmodifiableIterable<?>) {
             return iterable;
         }
-        @SuppressWarnings("unchecked") // safe
-        final Iterable<E> it = iterable != null ? iterable : EMPTY_ITERABLE;
-        return new UnmodifiableIterable<E>(it);
+        return new UnmodifiableIterable<E>(emptyIfNull(iterable));
     }
 
     /**
@@ -521,7 +518,7 @@ public class IterableUtils {
                 for (int i = 0; i < iterables.length; i++) {
                     iterators[i] = emptyIteratorIfNull(iterables[i]);
                 }
-                return new ZippingIterator<E>(iterators);
+                return IteratorUtils.zippingIterator(iterators);
             }
         };
     }
@@ -529,6 +526,18 @@ public class IterableUtils {
     // Utility methods
     // ----------------------------------------------------------------------
 
+    /**
+     * Returns an immutable empty iterable if the argument is null,
+     * or the argument itself otherwise.
+     *
+     * @param <E> the element type
+     * @param iterable  the iterable, may be null
+     * @return an empty iterable if the argument is null
+     */
+    public static <E> Iterable<E> emptyIfNull(final Iterable<E> iterable) {
+        return iterable == null ? IterableUtils.<E>emptyIterable() : iterable;
+    }
+
     /**
      * Returns an empty iterator if the argument is <code>null</code>,
      * or returns {@code iterable.iterator()} otherwise.