src/java.base/share/classes/java/lang/ref/ReferenceQueue.java

8203327: Small cleanups in java.lang.ref
Reviewed-by: mr

*** 41,61 ****
      /**
       * Constructs a new reference-object queue.
       */
      public ReferenceQueue() { }
  
!     private static class Null<S> extends ReferenceQueue<S> {
!         boolean enqueue(Reference<? extends S> r) {
              return false;
          }
      }
  
!     static ReferenceQueue<Object> NULL = new Null<>();
!     static ReferenceQueue<Object> ENQUEUED = new Null<>();
  
      private static class Lock { };
!     private Lock lock = new Lock();
      private volatile Reference<? extends T> head;
      private long queueLength = 0;
  
      boolean enqueue(Reference<? extends T> r) { /* Called only by Reference class */
          synchronized (lock) {
--- 41,61 ----
      /**
       * Constructs a new reference-object queue.
       */
      public ReferenceQueue() { }
  
!     private static class Null extends ReferenceQueue<Object> {
!         boolean enqueue(Reference<?> r) {
              return false;
          }
      }
  
!     static final ReferenceQueue<Object> NULL = new Null();
!     static final ReferenceQueue<Object> ENQUEUED = new Null();
  
      private static class Lock { };
!     private final Lock lock = new Lock();
      private volatile Reference<? extends T> head;
      private long queueLength = 0;
  
      boolean enqueue(Reference<? extends T> r) { /* Called only by Reference class */
          synchronized (lock) {