DiskQueue extends AbstractQueue<String> { @Override public String peek() { loadMemoryQueue(); return memoryQueue.peek(); } DiskQueue(int maxInMemorySize);  DiskQueue(int maxInMemorySize, File tempDir); @Override Iterator<String> iterator(); @Override int size(); @Override boolean offer(String element); @Override String peek(); @Override String remove(); @Override String poll(); @Override void clear();  }
@Test public void testPeek() { Queue<String> instance = new DiskQueue<String>(1); assertNull(instance.peek()); String item = "testPeek"; instance.add(item); assertEquals(item, instance.peek()); }