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add object into GSON array android studio

hey guys im using android's gson library to parse my JSON. everything is working fine in that I have that selected goal array sometimes it is full of values and sometimes it is an empty array. when array is empty I want to push an object init when I try to add its index
selected_goal.add(INDEX,VALUE)
I want to push an object at the place of value please help me how can I do it…
this is my pojo:
public class SelectedGoal {
#SerializedName("id")
#Expose
private String id;
#SerializedName("goal_name")
#Expose
private String goalName;
#SerializedName("image")
#Expose
private String image;
#SerializedName("position")
#Expose
private String position;
#SerializedName("athlete_id")
#Expose
private String athleteId;
#SerializedName("coach_id")
#Expose
private String coachId;
#SerializedName("current_goal_id")
#Expose
private String currentGoalId;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getGoalName() {
return goalName;
}
public void setGoalName(String goalName) {
this.goalName = goalName;
}
public String getImage() {
return image;
}
public void setImage(String image) {
this.image = image;
}
public String getPosition() {
return position;
}
public void setPosition(String position) {
this.position = position;
}
public String getAthleteId() {
return athleteId;
}
public void setAthleteId(String athleteId) {
this.athleteId = athleteId;
}
public String getCoachId() {
return coachId;
}
public void setCoachId(String coachId) {
this.coachId = coachId;
}
public String getCurrentGoalId() {
return currentGoalId;
}
public void setCurrentGoalId(String currentGoalId) {
this.currentGoalId = currentGoalId;
}
}

selected_goal.add(INDEX,new SelectedGoal());
EDIT- To set values, make constuctor in your SelectedGoal class like.
public SelectedGoal(String id, String goalName, String image, String
position, String athleteId, String coachId, String currentGoalId) {
this.id = id;
this.goalName = goalName;
this.image = image;
this.position = position;
this.athleteId = athleteId;
this.coachId = coachId;
this.currentGoalId = currentGoalId;
}
finally add your object into list like..
selected_goal.add(INDEX,new SelectedGoal(id,goalName,image,position,athleteId,coachId,currentGoalId));

Model structure to parse JSON with Retrofit [duplicate]

This question already has answers here:
Why does Gson fromJson throw a JsonSyntaxException: Expected BEGIN_OBJECT but was BEGIN_ARRAY?
(2 answers)
GSON throwing "Expected BEGIN_OBJECT but was BEGIN_ARRAY"?
(11 answers)
Closed 4 years ago.
I have the following JSON structure:
[
{
"id":1,
"name":"car",
"elements":[
{
"id":1,
"name":"price",
"type":"textField",
"constraints":"blablabla"
},
{
"id":2,
"name":"color",
"type":"textField",
"constraints":"blablabla"
},
{
"id":3,
"name":"images",
"type":"image",
"constraints":"blablabla"
}
]
}
]
And I have the following models:
public class Product {
private Long id;
private String name;
#Expose
private Element elements;
public Product(Long id, String name, Element elements) {
this.id = id;
this.name = name;
this.elements = elements;
}
public Long getId() {
return id;
}
public String getName() {
return name;
}
public Element getElements() {
return elements;
}
}
public class Element {
private Long id;
private String name;
private String type;
private String constraints;
public Element(Long id, String name, String constraints, String type) {
this.id = id;
this.type=type;
this.name = name;
this.constraints = constraints;
}
public String getType() {
return type;
}
public Long getId() {
return id;
}
public String getName() {
return name;
}
public String getConstraints() {
return constraints;
}
}
The Elements model is which I have problems, I am getting the following error:
ERROR: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 35 path $[0].elements
How can I change the model to make it work? I tried to change the elements in Product class to JSONObject array but when I wanted to parse, it was empty.

You need to modify your POJOs like this:
Element.java
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Element {
#SerializedName("id")
#Expose
private Integer id;
#SerializedName("name")
#Expose
private String name;
#SerializedName("type")
#Expose
private String type;
#SerializedName("constraints")
#Expose
private String constraints;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getConstraints() {
return constraints;
}
public void setConstraints(String constraints) {
this.constraints = constraints;
}
}
Product.java
import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
public class Product {
#SerializedName("id")
#Expose
private Integer id;
#SerializedName("name")
#Expose
private String name;
#SerializedName("elements")
#Expose
private List<Element> elements = null;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Element> getElements() {
return elements;
}
public void setElements(List<Element> elements) {
this.elements = elements;
}
}
P.S: You should use 'http://www.jsonschema2pojo.org/' website for generating POJO automatically from the JSON string you provide to it.
I hope this helps.

I think you try to put an array of Elements into "private Element elements" which is a single object

Change your pojo with this. Also you can add your respective constructor which you require.
public class Element {
#SerializedName("id")
#Expose
private Integer id;
#SerializedName("name")
#Expose
private String name;
#SerializedName("type")
#Expose
private String type;
#SerializedName("constraints")
#Expose
private String constraints;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getConstraints() {
return constraints;
}
public void setConstraints(String constraints) {
this.constraints = constraints;
}
}
public class Product {
#SerializedName("id")
#Expose
private Integer id;
#SerializedName("name")
#Expose
private String name;
#SerializedName("elements")
#Expose
private List<Element> elements = null;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Element> getElements() {
return elements;
}
public void setElements(List<Element> elements) {
this.elements = elements;
}
}

in json you have list of Element and in the model you declared Element as an Object
change this private Element elements; to List of Element

Try this pojo or you can make from this link
private String id;
private String name;
private ArrayList<Elements> elements;
public String getId ()
{
return id;
}
public void setId (String id)
{
this.id = id;
}
public String getName ()
{
return name;
}
public void setName (String name)
{
this.name = name;
}
public ArrayList<Elements> getElements ()
{
return elements;
}
public void setElements (ArrayList<Elements> elements)
{
this.elements = elements;
}
#Override
public String toString()
{
return "ClassPojo [id = "+id+", name = "+name+", elements = "+elements+"]";
}
public class Elements
{
private String id;
private String name;
private String constraints;
private String type;
public String getId ()
{
return id;
}
public void setId (String id)
{
this.id = id;
}
public String getName ()
{
return name;
}
public void setName (String name)
{
this.name = name;
}
public String getConstraints ()
{
return constraints;
}
public void setConstraints (String constraints)
{
this.constraints = constraints;
}
public String getType ()
{
return type;
}
public void setType (String type)
{
this.type = type;
}
#Override
public String toString()
{
return "ClassPojo [id = "+id+", name = "+name+", constraints = "+constraints+",
type = "+type+"]";
}
}

How to retrieve a value from list android

I have a list specialties having 75 items that has two values id and name.
private List specialties;
I would like to get the name without using a loop something like below
specialties.get(0).name;
I get an error saying can't resolve name. Is there any way to retrieve name from the values list.
Thanks.

Create a class (Model) to get and set the ID and Name property:-
public class ClassName {
private String id;
private String name;
public ClassName(String mId, String mName){
this.id=mId;
this.name=mName;
}
public String getName() {
return name;
}
public void setName(String sName) {
this.name = sName;
}
public String getId() {
return id;
}
public void setId(String sId) {
this.id = sId;
}
}
In your Activity:-
Define a List having the ClassName type of objects.
List<ClassName> mList = new ArrayList<>();
Now access the property name like this:-
mList.get(0).getName();
mList.get(0).getId();

try the following:
public class Clone {
private int Id;
private String name;
public int getId() {
return Id;
}
public String getName() {
return name;
}
public void setId(int id) {
Id = id;
}
public void setName(String name) {
this.name = name;
}
}
and use
private List<Clone> arrayList = new ArrayList();
for (int i = 0; i < 10; i++) {
Clone helloItem = new Clone();
helloItem.setId(i);
helloItem.setName("I'm Clone no - " + i);
arrayList.add(helloItem);
}
Log.d("check", "get item - " + arrayList.get(0).getName());
hope it help.

I want to suggest you. You should declare name with public access. If it is not public, use public getter and setter method.Call getName() method.
public class YourClass{
private int id;
private String name;
public YourClass(int id, String name) {
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
private List<YourClass> specialties = new ArrayList<YourClass>;
...//add data into list...
specialties.add(new YourClass( 1 , "John"));
...// retrieve data
specialties.get(position).getName();

You have declared your list as private List specialties; you can not access it like this specialties.get(0).name;
You need declare your list like this private List<YourModelClass> specialties;
SAMPLE DEMO
If you want add model class in your list than than check this example
create model class like this
public class User {
String name, email;
public User(String name, String email) {
this.name = name;
this.email = email;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
Now use like this in your list
List<User> userArrayList= new ArrayList<>();
To add data inside list like this
userArrayList.add(new User("Nilesh","abc#gmail.com"));
To get data from your list use like this
userArrayList.get(0).getEmail();
userArrayList.get(0).getEmail();
or
for (int i=0;i<userArrayList.size();i++){
userArrayList.get(i).getName();
userArrayList.get(i).getEmail();
}

Realm: How can I set an int to nullable, so that if it gets the value "null" back from the json, it can be ignored

I have the following object:
#RealmClass
public class TripStop extends RealmObject implements Serializable {
#Nullable
private int arrival_time;
private String address;
#PrimaryKey
private int id;
#Nullable
private int departure_time;
private Destination place;
private CoordLocation location;
public int getArrival_time() {
return arrival_time;
}
public void setArrival_time(int arrival_time) {
this.arrival_time = arrival_time;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getDeparture_time() {
return departure_time;
}
public void setDeparture_time(int departure_time) {
this.departure_time = departure_time;
}
public Destination getPlace() {
return place;
}
public void setPlace(Destination place) {
this.place = place;
}
public CoordLocation getLocation() {
return location;
}
public void setLocation(CoordLocation location) {
this.location = location;
}
}
But everytime I get a json response back, with an int (or primitive) as null, I get an error in Realm that:
08-29 16:45:59.220: I/WSCalls(6370): error :Trying to set non-nullable field 'departure_time' to null.
I read that from Realm 3.5 it is possible to set null values, or set a default version, but I did not manage yet.
How is that possible? I see that the #Nullable does not help

First of all:
int is a primitive data type and cannot be assigend with null.
Solution:
You can change the type to Integer. An Integer can contain null, but it adds a little overhead because of boxing/unboxing.
(see: https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html)

Using Gson to parse string to object. Boolean value is always false

I fecht a Json-String from my server:
{"erfolgreich":"true","id":"14"}
When I call
//result is the string above
msgServer = gson.fromJson(result, MsgSpielerErstellenSA.class);
The boolean is always false...
What am I doing wrong?
Here is my MsgSpielerErstellenSA
public class MsgSpielerErstellenSA {
private long id;
private boolean isErfolgreich;
public MsgSpielerErstellenSA(long id, boolean isErfolgreich) {
super();
this.id = id;
this.isErfolgreich = isErfolgreich;
}
public boolean isErfolgreich() {
return isErfolgreich;
}
public void setErfolgreich(boolean isErfolgreich) {
this.isErfolgreich = isErfolgreich;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
}

Because the correct name for the boolean field is erfolgreich, not isErfolgreich. Please use the following class:
public class MsgSpielerErstellenSA {
private long id;
private boolean erfolgreich;
public MsgSpielerErstellenSA(long id, boolean isErfolgreich) {
this.id = id;
this.erfolgreich = isErfolgreich;
}
public boolean isErfolgreich() {
return erfolgreich;
}
public void setErfolgreich(boolean isErfolgreich) {
this.erfolgreich = isErfolgreich;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
}
But if you don't want to rename this field, you can use #SerializedName("erfolgreich") annotation on it

The name of your key "erfolgreich" in json string should be same as your class data member "isErfolgreich" or you should use #SerializedName notation before define your member. if gson can not match between a class member and json keys, then use the default value for that member type. so you can use the nikis solution or you can use notation like this:
#SerializedName("erfolgreich")
private boolean isErfolgreich;