8292317: Missing null check for Iterator.forEachRemaining implementations

Reviewed-by: sundar, smarks

Author: jaikiran

src/java.base/share/classes/java/util/Collections.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2022, 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
@@ -1714,6 +1714,7 @@ public void remove() {
                         throw new UnsupportedOperationException();
                     }
                     public void forEachRemaining(Consumer<? super Map.Entry<K, V>> action) {
+                        Objects.requireNonNull(action);
                         i.forEachRemaining(entryConsumer(action));
                     }
                 };
@@ -3878,6 +3879,7 @@ public Map.Entry<K,V> next() {
                     }
 
                     public void forEachRemaining(Consumer<? super Entry<K, V>> action) {
+                        Objects.requireNonNull(action);
                         i.forEachRemaining(
                             e -> action.accept(checkedEntry(e, valueType)));
                     }

test/jdk/java/util/Collections/DelegatingIteratorForEachRemaining.java

@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2018, 2022, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2018 Google Inc. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
@@ -195,4 +196,29 @@ private static Map<String, Object> map() {
         Class clazz = entrySet.iterator().next().getClass();
         assertThrowingIterator(Collections.checkedSet(entrySet, clazz).iterator());
     }
+
+    /**
+     * Calls Collections.unmodifiableMap().entrySet().iterator().forEachRemaining() by passing
+     * that method a {@code null} action and expects that call to fail with a
+     * {@code NullPointerException}.
+     */
+    @Test
+    public void testUnmodifiableForEachRemainingNPE() {
+        final Iterator<?> it = Collections.unmodifiableMap(Map.of()).entrySet().iterator();
+        // pass null action and expect a NPE
+        Assert.assertThrows(NullPointerException.class, () -> it.forEachRemaining(null));
+    }
+
+    /**
+     * Calls Collections.checkedMap().entrySet().iterator().forEachRemaining() by passing
+     * that method a {@code null} action and expects that call to fail with a
+     * {@code NullPointerException}.
+     */
+    @Test
+    public void testCheckedMapForEachRemainingNPE() {
+        final Iterator<?> it = Collections.checkedMap(Map.of(), String.class,
+                String.class).entrySet().iterator();
+        // pass null "action" and expect it to fail with NPE
+        Assert.assertThrows(NullPointerException.class, () -> it.forEachRemaining(null));
+    }
 }