Deserialisation of YAML file with nested arrays in java

I'm trying to deserialise a Yaml file in Java but facing issues as it has nested array format in it like in below example.

items.yml

ITEMS:
  - item1
  - item2
  - item3:
    - item4
    - item5
  - item6

I'm using Jackson here to deserialise it and it is working fine till item2 but while deserialising item3 it is throwing below exception:

com.fasterxml.jackson.databind.JsonMappingException: No suitable constructor found for type [simple type, class com.ymalParser.io.Item]: can not instantiate from JSON object (need to add/enable type information?)

I'm new to this deserialisation thing.
Can anyone help me with what I'm missing here.

Thanks in advance..

You are creating an array of simple types (item1, item2, item6). However item3 is a complex type.

ITEMS:
  - item1
  - item2
...

Can be serialized in to List<String>

ITEMS:
  - item1
  - item2
  - item3:
    - item4
    - item5
  - item6

Can not be serialized in to List<String> but Map<String, List<Object>.

Try this one:

ITEMS:
  - item1: []
  - item2: []
  - item3:
    - item4
    - item5
  - item6: []

SECOND EDIT:

public void test() {
	ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
	Resource resource = new ClassPathResource("test.yaml");
	InputStream input = resource.getInputStream();
	Map<String, List<Object>> list = mapper.readValue(input, new TypeReference<Map<String, List<Object>>>() {});
	mapper.writeValue(System.out, list);
}

Outputs:

---
ITEMS:
- "item1"
- "item2"
- item3:
  - "item4"
  - "item5"
- "item6"

I'm not going to provide an answer, just a small hint: see how your data looks like when converted to JSON:

{
   "ITEMS": [
      "item1",
      "item2",
      {
         "item3": [
            "item4",
            "item5"
         ]
      },
      "item6"
   ]
}

The problem is that the elements of the ITEMS array are of different types: item1, item2 and item6 are strings, the third item is an object. In theory it's valid YAML/JSON, but deserializing it to a java object is problematic.