Instead of using JSONObject you may use JSONArray. If you really need to convert it to a List you may do something like:

List<JSONObject> list = new ArrayList<JSONObject>();
try {
    int i;
    JSONArray array = new JSONArray(string);
    for (i = 0; i < array.length(); i++)
        list.add(array.getJSONObject(i);
} catch (JSONException e) {
    System.out.println(e.getMessage());
}

You are asking Jackson to parse a StudentList. Tell it to parse a List (of students) instead. Since List is generic you will typically use a TypeReference

List<Student> participantJsonList = mapper.readValue(jsonString, new TypeReference<List<Student>>(){});

You can convert the result to an object list, or you can pass in a type parameter rather than the List class.

String jsonString = "[{\"id\": \"0\", \"ip\": \"123\", \"mac\": \"456\"}, {\"id\": \"1\", \"ip\": \"111\", \"mac\": \"222\"}]";

With Object

List<Object> items = objectMapper.readValue(
    jsonString,
    objectMapper.getTypeFactory().constructParametricType(List.class, Object.class)
);

With SlaveEntity

List<SlaveEntity> items = objectMapper.readValue(
    jsonString,
    objectMapper.getTypeFactory().constructCollectionType(List.class, SlaveEntity.class)
);

Update

This is what I have come up with, and it works.

EntityTest

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.databind.ObjectMapper;

public class EntityTest {
    public static void main(String[] args) {
        String json = "[{\"id\": \"0\", \"ip\": \"123\", \"mac\": \"456\"}, {\"id\": \"1\", \"ip\": \"111\", \"mac\": \"222\"}]";

        for (SlaveEntity entity : jsonToSlaveEntity(json)) {
            System.out.println(entity);
        }
    }

    public static List<SlaveEntity> jsonToSlaveEntity(String json) {
        ObjectMapper objectMapper = new ObjectMapper();

        try {
           return objectMapper.readValue(
                   json,
                objectMapper.getTypeFactory().constructCollectionType(List.class, SlaveEntity.class)
            );

        } catch (IOException e) {
            e.printStackTrace();
        }
        return new ArrayList<SlaveEntity>();
    }
}

BaseEntity

public class BaseEntity {
    private long id;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }
}

SlaveEntity

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.FetchType;
import javax.persistence.OneToMany;

import com.fasterxml.jackson.annotation.JsonProperty;

public class SlaveEntity extends BaseEntity {
    private String ip;

    @JsonProperty("mac")
    private String macAddress;

    private String status;

    @OneToMany(mappedBy = "slave", targetEntity = PositionEntity.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private List<PositionEntity> positions;

    public String getIp() {
        return ip;
    }

    public void setIp(String ip) {
        this.ip = ip;
    }

    public String getMacAddress() {
        return macAddress;
    }

    public void setMacAddress(String macAddress) {
        this.macAddress = macAddress;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public List<PositionEntity> getPositions() {
        return positions;
    }

    public void setPositions(List<PositionEntity> positions) {
        this.positions = positions;
    }

    @Override
    public String toString() {
        return String.format(
                "SlaveEntity [id=%d, ip=%s, mac=%s, status=%s, positions=%s]",
                getId(), ip, macAddress, status, positions);
    }
}

PositionEntity

public class PositionEntity {
    // ?
}

Result

SlaveEntity [id=0, ip=123, mac=456, status=null, positions=null]
SlaveEntity [id=1, ip=111, mac=222, status=null, positions=null]

The problem is not in your code but in your json:

{"Compemployes":[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]}

this represents an object which contains a property Compemployes which is a list of Employee. In that case you should create that object like:

class EmployeList{
    private List<Employe> compemployes;
    (with getter an setter)
}

and to deserialize the json simply do:

EmployeList employeList = mapper.readValue(jsonString,EmployeList.class);

If your json should directly represent a list of employees it should look like:

[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]

Last remark:

List<Employee> list2 = mapper.readValue(jsonString, 
TypeFactory.collectionType(List.class, Employee.class));

TypeFactory.collectionType is deprecated you should now use something like:

List<Employee> list = mapper.readValue(jsonString,
TypeFactory.defaultInstance().constructCollectionType(List.class,  
   Employee.class));

There are two problems with your code :

1. First is that you are using a getJsonArray() to get the array, which isn't part of Gson library, you need to use getAsJsonArray() method instead.
2. Second is that you are using array.toString() which isn't obvious because for the fromJson method you need a jsonArray as parameter and not String and that will cause you parse problems, just remove it.

And use the following code to convert your jsonArray to List<Noticia> :

Type type = new TypeToken<List<Noticia>>() {}.getType();
List<Noticia> lista = gson.fromJson(array, type);

And your whole code will be:

Gson gson = new Gson();
JSONArray array = obj.getAsJsonArray("result");

Type type = new TypeToken<List<Noticia>>() {}.getType();
List<Noticia> lista = gson.fromJson(array, type);

//testing - size = 2 but value Titulo is null
Log.i("LISTSIZE->", lista.size() +"");
for(Noticia n:lista){
   Log.i("TITULO", n.getTitulo());
}

Your root JSON is an Array, so first create a JSONArray from your String.

Do this:

JSONArray arr = new JSONArray(jstring);
for (int i = 0; i < arr.length(); i++) { // Walk through the Array.
    JSONObject obj = arr.getJSONObject(i);
    JSONArray arr2 = obj.getJSONArray("fileName");
    // Do whatever.
}

For more info, please refer to the docs on JSONArray and JSONObject.