@Test
public void toJSONString() throws Exception {

    Assert.assertEquals(JSONUtils.toJSONString("xxx"), "\"xxx\"");
    Assert.assertEquals(JSONUtils.toJSONString(1), "1");
    Assert.assertEquals(JSONUtils.toJSONString(2.2d), "2.2");
    Assert.assertEquals(JSONUtils.toJSONString(false), "false");
    Assert.assertEquals(JSONUtils.toJSONString(new HashMap()), "{}");
    Assert.assertEquals(JSONUtils.toJSONString(new ArrayList()), "[]");
    Assert.assertEquals(JSONUtils.toJSONString(new Object[0]), "[]");
}