From 4c999ed180fa9937db895c2aa432db496f2ee63e Mon Sep 17 00:00:00 2001
From: Doug Lea <dl@openjdk.org>
Date: Wed, 24 Aug 2016 12:50:37 -0700
Subject: [PATCH] 8163353: NPE in ConcurrentHashMap.removeAll()

Reviewed-by: martin, psandoz, redestad, alanb
---
 .../java/util/concurrent/ConcurrentHashMap.java   |  5 ++++-
 .../concurrent/tck/ConcurrentHashMapTest.java     | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java b/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
index aadf3ca32a9..1d80077b58c 100644
--- a/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
+++ b/jdk/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
@@ -4566,7 +4566,10 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
             boolean modified = false;
             // Use (c instanceof Set) as a hint that lookup in c is as
             // efficient as this view
-            if (c instanceof Set<?> && c.size() > map.table.length) {
+            Node<K,V>[] t;
+            if ((t = map.table) == null) {
+                return false;
+            } else if (c instanceof Set<?> && c.size() > t.length) {
                 for (Iterator<?> it = iterator(); it.hasNext(); ) {
                     if (c.contains(it.next())) {
                         it.remove();
diff --git a/jdk/test/java/util/concurrent/tck/ConcurrentHashMapTest.java b/jdk/test/java/util/concurrent/tck/ConcurrentHashMapTest.java
index c521b7edd58..26095ad1bb0 100644
--- a/jdk/test/java/util/concurrent/tck/ConcurrentHashMapTest.java
+++ b/jdk/test/java/util/concurrent/tck/ConcurrentHashMapTest.java
@@ -359,6 +359,21 @@ public class ConcurrentHashMapTest extends JSR166TestCase {
         assertTrue(s.contains(five));
     }
 
+    /**
+     * Test keySet().removeAll on empty map
+     */
+    public void testKeySet_empty_removeAll() {
+        ConcurrentHashMap<Integer, String> map = new ConcurrentHashMap<>();
+        Set<Integer> set = map.keySet();
+        set.removeAll(Collections.emptyList());
+        assertTrue(map.isEmpty());
+        assertTrue(set.isEmpty());
+        // following is test for JDK-8163353
+        set.removeAll(Collections.emptySet());
+        assertTrue(map.isEmpty());
+        assertTrue(set.isEmpty());
+    }
+
     /**
      * keySet.toArray returns contains all keys
      */