[COLLECTIONS-710] Calling CompositeCollection.size() will cash if the

list contains null element.

src/main/java/org/apache/commons/collections4/set/CompositeSet.java

@@ -252,6 +252,9 @@ public class CompositeSet<E> implements Set<E>, Serializable {
      */
     @Override
     public boolean containsAll(final Collection<?> coll) {
+        if (coll == null) {
+            return false;
+        }
         for (final Object item : coll) {
             if (contains(item) == false) {
                 return false;
@@ -291,7 +294,7 @@ public class CompositeSet<E> implements Set<E>, Serializable {
      */
     @Override
     public boolean removeAll(final Collection<?> coll) {
-        if (coll.size() == 0) {
+        if (CollectionUtils.isEmpty(coll)) {
             return false;
         }
         boolean changed = false;
@@ -354,6 +357,7 @@ public class CompositeSet<E> implements Set<E>, Serializable {
      * @see SetMutator
      */
     public synchronized void addComposited(final Set<E> set) {
+        if (set != null) {
             for (final Set<E> existingSet : getSets()) {
                 final Collection<E> intersects = CollectionUtils.intersection(existingSet, set);
                 if (intersects.size() > 0) {
@@ -370,6 +374,7 @@ public class CompositeSet<E> implements Set<E>, Serializable {
             }
             all.add(set);
         }
+    }
 
     /**
      * Add these Sets to the list of sets in this composite.
@@ -388,10 +393,12 @@ public class CompositeSet<E> implements Set<E>, Serializable {
      * @param sets  the Sets to be appended to the composite
      */
     public void addComposited(final Set<E>... sets) {
+        if (sets != null) {
             for (final Set<E> set : sets) {
                 addComposited(set);
             }
         }
+    }
 
     /**
      * Removes a set from those being decorated in this composite.

src/test/java/org/apache/commons/collections4/set/CompositeSetTest.java

@@ -64,6 +64,18 @@ public class CompositeSetTest<E> extends AbstractSetTest<E> {
         assertTrue(set.contains("1"));
     }
 
+    @SuppressWarnings("unchecked")
+    public void testContainsAll() {
+        final CompositeSet<E> set = new CompositeSet<>(new Set[]{ buildOne(), buildTwo() });
+        assertFalse(set.containsAll(null));
+    }
+
+    @SuppressWarnings("unchecked")
+    public void testRemoveAll() {
+        final CompositeSet<E> set = new CompositeSet<>(new Set[]{ buildOne(), buildTwo() });
+        assertFalse(set.removeAll(null));
+    }
+
     @SuppressWarnings("unchecked")
     public void testRemoveUnderlying() {
         final Set<E> one = buildOne();
@@ -132,6 +144,10 @@ public class CompositeSetTest<E> extends AbstractSetTest<E> {
         final Set<E> two = buildTwo();
         final CompositeSet<E> set = new CompositeSet<>();
         set.addComposited(one, two);
+        set.addComposited((Set<E>) null);
+        set.addComposited((Set<E>[]) null);
+        set.addComposited(null, null);
+        set.addComposited(null, null, null);
         final CompositeSet<E> set2 = new CompositeSet<>(buildOne());
         set2.addComposited(buildTwo());
         assertTrue(set.equals(set2));