@Test
public void testJsonArray() throws Exception {

    LOG.info("testJsonArray");
    final int[] x = {1, 2, 3};
    final String s1 = Json.toJson(x);
    LOG.info("x.toJson = {}", s1);
    Assert.assertEquals("[1,2,3]", s1);
    final ArrayList<Integer> y = new ArrayList<>();
    y.add(10);
    y.add(20);
    y.add(30);
    final String s2 = Json.toJson(y);
    LOG.info("y.toJson = {}", s2);
    Assert.assertEquals("[10,20,30]", s2);
    final List<List<Integer>> z = new ArrayList<>();
    final List<Integer> a = new ArrayList<>();
    a.add(10);
    a.add(20);
    a.add(30);
    final List<Integer> b = new ArrayList<>();
    b.add(100);
    final List<Integer> c = Collections. EMPTY_LIST;
    z.add(a);
    z.add(b);
    z.add(c);
    final String s3 = Json.toJson(z);
    LOG.info("z.toJson = {}", s3);
    Assert.assertEquals("[[10,20,30],[100],[]]", s3);
}