{
  "foo": "bar",
  "baz": [ "qux","quxx"],
  "corge": null,
  "grault": 1,
  "garply": true,
  "waldo": "false",
  "fred": "undefined",
  "emptyArray": [],
  "emptyObject": {},
  "emptyString": ""
}

foo: "bar"
baz:
  - "qux"
  - "quxx"
corge: null
grault: 1
garply: true
waldo: "false"
fred: "undefined"
emptyArray: []
emptyObject: {}
emptyString: ""

import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLMapper;

public class Library {

    public String asYaml(String jsonString) throws JsonProcessingException, IOException {
        // parse JSON
        JsonNode jsonNodeTree = new ObjectMapper().readTree(jsonString);
        // save it as YAML
        String jsonAsYaml = new YAMLMapper().writeValueAsString(jsonNodeTree);
        return jsonAsYaml;
    }

}

compile 'com.fasterxml.jackson.core:jackson-core:2.8.6'
compile 'com.fasterxml.jackson.core:jackson-databind:2.8.6'
compile 'com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:2.8.6'

// this is your json object
  JSONObject jsonobject = new JSONObject(map);
  // get json string
  String prettyJSONString = jsonobject.toString(4);
  // mapping
  Map<String,Object> map = (Map<String, Object>) yaml.load(prettyJSONString);
  // convert to yaml string (yaml formatted string)
  String output = yaml.dump(map2);