@Test public void testSerialization2() throws IOException, ClassNotFoundException { final MutableRoaringBitmap rr = new MutableRoaringBitmap(); for (int k = 200; k < 400; ++k) rr.add(k); final ByteArrayOutputStream bos = new ByteArrayOutputStream(); // Note: you could use a file output steam instead of // ByteArrayOutputStream final ObjectOutputStream oo = new ObjectOutputStream(bos); rr.writeExternal(oo); oo.close(); final MutableRoaringBitmap rrback = new MutableRoaringBitmap(); final ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray()); rrback.readExternal(new ObjectInputStream(bis)); Assert.assertEquals(rr.getCardinality(), rrback.getCardinality()); Assert.assertTrue(rr.equals(rrback)); }