Add support for deque interface

src/main/java/org/apache/commons/collections4/deque/BlockingDeque.java

@@ -40,6 +40,10 @@ import java.util.concurrent.locks.ReentrantLock;
  * @since 4.5
  */
 public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>, Serializable {
+
+    /** Serialization version */
+    private static final long serialVersionUID = 3961982897426944557L;
+
     final Deque<E> deque;
     final ReentrantLock lock = new ReentrantLock();
 
@@ -116,7 +120,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.offerFirst(e)) == true)
+            if (r = deque.offerFirst(e))
                 notEmpty.signal();
             return r;
         } catch (Exception ex) {
@@ -139,7 +143,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.offerLast(e)) == true)
+            if (r = deque.offerLast(e))
                 notEmpty.signal();
             return r;
         } catch (Exception ex) {
@@ -330,7 +334,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.removeFirstOccurrence(o)) == true)
+            if (r = deque.removeFirstOccurrence(o))
                 notEmpty.signal();
             return r;
         } finally {
@@ -343,7 +347,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.removeLastOccurrence(o)) == true)
+            if (r = deque.removeLastOccurrence(o))
                 notEmpty.signal();
             return r;
         } finally {
@@ -412,7 +416,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.addAll(c)) == true)
+            if (r = deque.addAll(c))
                 notEmpty.signalAll();
             return r;
         } finally {
@@ -425,7 +429,7 @@ public class BlockingDeque<E> extends AbstractCollection<E> implements Deque<E>,
         lock.lock();
         try {
             boolean r;
-            if ((r = deque.removeAll(c)) == true)
+            if (r = deque.removeAll(c))
                 notFull.signalAll();
             return r;
         } finally {

src/main/java/org/apache/commons/collections4/deque/CircularDeque.java

@@ -56,6 +56,9 @@ import java.util.Iterator;
 public class CircularDeque<E> extends AbstractCollection<E>
         implements Deque<E>, BoundedCollection<E>, Serializable {
 
+    /** Serialization version */
+    private static final long serialVersionUID = 6013343683263686185L;
+
     /** Underlying storage array. */
     private transient E[] elements;
 
@@ -469,7 +472,7 @@ public class CircularDeque<E> extends AbstractCollection<E>
                 System.arraycopy(elements, i + 1, elements, i, back);
                 tail--;
             }
-        } else if (head >tail) {
+        } else if (head > tail) {
             if (i > head) {
                 System.arraycopy(elements, head, elements, head + 1, front);
                 head++;

src/main/java/org/apache/commons/collections4/deque/PredicatedDeque.java

@@ -40,6 +40,10 @@ import java.util.Iterator;
  * @since 4.5
  */
 public class PredicatedDeque<E> extends PredicatedCollection<E> implements Deque<E> {
+
+    /** Serialization version */
+    private static final long serialVersionUID = 7027705675493389763L;
+
     /**
      * Factory method to create a predicated (validating) deque.
      * <p>

src/main/java/org/apache/commons/collections4/deque/SynchronizedDeque.java

@@ -34,7 +34,7 @@ import java.util.Iterator;
 public class SynchronizedDeque<E> extends SynchronizedCollection<E> implements Deque<E> {
 
     /** Serialization version */
-    private static final long serialVersionUID = 1L;
+    private static final long serialVersionUID = 4565577797338001569L;
 
     /**
      * Factory method to create a synchronized deque.

src/main/java/org/apache/commons/collections4/deque/TransformedDeque.java

@@ -39,7 +39,7 @@ import java.util.Iterator;
 public class TransformedDeque<E> extends TransformedCollection<E> implements Deque<E> {
 
     /** Serialization version */
-    private static final long serialVersionUID = -7901091318986132033L;
+    private static final long serialVersionUID = 7959728067506831816L;
 
     /**
      * Factory method to create a transforming deque.
@@ -76,7 +76,7 @@ public class TransformedDeque<E> extends TransformedCollection<E> implements Deq
      */
     public static <E> TransformedDeque<E> transformedDeque(final Deque<E> deque,
                                                            final Transformer<? super E, ? extends E> transformer) {
-        // throws IAE if deque or transformer is null
+        // throws NullPointerException if deque or transformer is null
         final TransformedDeque<E> decorated = new TransformedDeque<>(deque, transformer);
         if (deque.size() > 0) {
             @SuppressWarnings("unchecked") // deque is type <E>

src/test/java/org/apache/commons/collections4/deque/AbstractDequeTest.java

@@ -750,8 +750,8 @@ public abstract class AbstractDequeTest<E> extends AbstractCollectionTest<E> {
             return;
         }
 
-        final byte[] objekt = writeExternalFormToBytes((Serializable) deque);
+        final byte[] object = writeExternalFormToBytes((Serializable) deque);
-        final Deque<E> deque2 = (Deque<E>) readExternalFormFromBytes(objekt);
+        final Deque<E> deque2 = (Deque<E>) readExternalFormFromBytes(object);
 
         assertEquals("Both deques are empty", 0, deque.size());
         assertEquals("Both deques are empty", 0, deque2.size());
@@ -765,8 +765,8 @@ public abstract class AbstractDequeTest<E> extends AbstractCollectionTest<E> {
             return;
         }
 
-        final byte[] objekt = writeExternalFormToBytes((Serializable) deque);
+        final byte[] object = writeExternalFormToBytes((Serializable) deque);
-        final Deque<E> deque2 = (Deque<E>) readExternalFormFromBytes(objekt);
+        final Deque<E> deque2 = (Deque<E>) readExternalFormFromBytes(object);
 
         assertEquals("Both deques are same size", size, deque.size());
         assertEquals("Both deques are same size", size, deque2.size());

src/test/java/org/apache/commons/collections4/deque/CircularDequeTest.java

@@ -81,10 +81,10 @@ public class CircularDequeTest<E> extends AbstractDequeTest<E> {
     public void testConstructorException1() {
         try {
             new CircularDeque<E>(0);
+            fail();
         } catch (final IllegalArgumentException ex) {
-            return;
+
         }
-        fail();
     }
 
     /**
@@ -93,10 +93,10 @@ public class CircularDequeTest<E> extends AbstractDequeTest<E> {
     public void testConstructorException2() {
         try {
             new CircularDeque<E>(-20);
+            fail();
         } catch (final IllegalArgumentException ex) {
-            return;
+
         }
-        fail();
     }
 
     /**
@@ -105,10 +105,10 @@ public class CircularDequeTest<E> extends AbstractDequeTest<E> {
     public void testConstructorException3() {
         try {
             new CircularDeque<E>(null);
+            fail();
         } catch (final NullPointerException ex) {
-            return;
+
         }
-        fail();
     }
 
     /**