@Test public void testForEachKey() { final IntArrayList keys = new IntArrayList(); OpenIntLongHashMap map = new OpenIntLongHashMap(); map.put((int) 11, (long) 22); map.put((int) 12, (long) 23); map.put((int) 13, (long) 24); map.put((int) 14, (long) 25); map.removeKey((int) 13); map.forEachKey(new IntProcedure() { @Override public boolean apply(int element) { keys.add(element); return true; } }); int[] keysArray = keys.toArray(new int[keys.size()]); Arrays.sort(keysArray); assertArrayEquals(new int[] {11, 12, 14}, keysArray ); }