### Question:
OffHeapFixedStack implements Stack { OffHeapFixedStack(long capacity, boolean fill) { _capacity = capacity; _next = POffHeapLongArray.allocate(capacity); _prev = POffHeapLongArray.allocate(capacity); this._first = -1; this._last = -1; if (fill) { for (long i = 0; i < capacity; i++) { long l = _last; POffHeapLongArray.set(_prev, i, l); _last = i; if (_first == -1) { _first = i; } else { POffHeapLongArray.set(_next, l, i); } } _count = capacity; } else { _count = 0; } } OffHeapFixedStack(long capacity, boolean fill); @Override synchronized final boolean enqueue(long index); @Override synchronized final long dequeueTail(); @Override synchronized final boolean dequeue(long index); @Override final void free(); @Override synchronized long size();  }### Answer:
@Test public void offHeapFixedStackTest() { Stack stack = new OffHeapFixedStack(CAPACITY, true); test(stack); stack.free(); if (OffHeapConstants.DEBUG_MODE) { Assert.assertEquals(OffHeapConstants.SEGMENTS.size(), 0); } }