Make internal classes final where possible

src/main/java/stormpot/internal/DirectAllocationController.java

@@ -25,7 +25,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
-public class DirectAllocationController<T extends Poolable> extends AllocationController<T> {
+public final class DirectAllocationController<T extends Poolable> extends AllocationController<T> {
   private final LinkedTransferQueue<BSlot<T>> live;
   private final RefillPile<T> disregardPile;
   private final BSlot<T> poisonPill;

src/main/java/stormpot/internal/InlineAllocationController.java

@@ -31,7 +31,7 @@
 
 import static java.util.Objects.requireNonNull;
 
-public class InlineAllocationController<T extends Poolable> extends AllocationController<T> {
+public final class InlineAllocationController<T extends Poolable> extends AllocationController<T> {
   private static final VarHandle SIZE;
   private static final VarHandle ALLOC_COUNT;
   private static final VarHandle FAILED_ALLOC_COUNT;

src/main/java/stormpot/internal/OrExpiration.java

@@ -31,7 +31,7 @@
  * @author Guillaume Lederrey
  * @since 2.4
  */
-public class OrExpiration<T extends Poolable> implements Expiration<T> {
+public final class OrExpiration<T extends Poolable> implements Expiration<T> {
   private final Expiration<T> firstExpiration;
   private final Expiration<T> secondExpiration;
 

src/main/java/stormpot/internal/PoolBuilderDefaults.java

@@ -20,7 +20,7 @@
 
 import java.util.concurrent.ThreadFactory;
 
-public class PoolBuilderDefaults {
+public final class PoolBuilderDefaults {
   public final Expiration<? super Poolable> expiration;
   public final ThreadFactory threadFactory;
   public final boolean preciseLeakDetectionEnabled;

src/main/java/stormpot/internal/RefillSlot.java

@@ -17,7 +17,7 @@
 
 import stormpot.Poolable;
 
-public class RefillSlot<T extends Poolable> {
+public final class RefillSlot<T extends Poolable> {
   final BSlot<T> slot;
   volatile RefillSlot<T> next;
 

src/main/java/stormpot/internal/ThreadedAllocationController.java

@@ -21,9 +21,10 @@
 import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.ThreadFactory;
 
-public class ThreadedAllocationController<T extends Poolable> extends AllocationController<T> {
+public final class ThreadedAllocationController<T extends Poolable> extends AllocationController<T> {
   private final BAllocThread<T> allocator;
   private final Thread allocatorThread;
+
   ThreadedAllocationController(
       LinkedTransferQueue<BSlot<T>> live,
       RefillPile<T> disregardPile,