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Global Variable appending multiple copies of data while updating

I have created a class named "Global Services" which I use to save my data globally and access them in a different activity. But when I am calling the set() method, instead of overview the existing data instead it is appending that data. Below is my code.
I have even tried to remove the instance but still, it is appending the new data instead of overwriting.
import java.util.ArrayList;
import java.util.List;
public class GlobalServices {
private static GlobalServices instance;
String partner, leadsResponse;
List<Leads> assignedList = new ArrayList<>();
List<Leads> unAssignedList = new ArrayList<>();
List<Inventory> listInventory = new ArrayList<>();
private GlobalServices() {}
public static GlobalServices getInstance() {
if (instance == null) {
instance = new GlobalServices();
}
return instance;
}
public static void destory() {
instance = null;
}
public String getPartner() {
return partner;
}
public String getLeadsResponse() {
return leadsResponse;
}
public List<Leads> getAssignedList() {
return assignedList;
}
public List<Leads> getUnAssignedList() {
return unAssignedList;
}
public List<Inventory> getListInventory() {
return listInventory;
}
public void setPartner(String partner) {
this.partner = partner;
}
public void setLeadsResponse(String leadsResponse) {
this.leadsResponse = leadsResponse;
}
public void setAssignedList(List<Leads> assignedList) {
this.assignedList = assignedList;
}
public void setUnAssignedList(List<Leads> unAssignedList) {
this.unAssignedList = unAssignedList;
}
public void setListInventory(List<Inventory> listInventory) {
this.listInventory = listInventory;
}
}

The problem is that you're just assigning new references to your lists in GlobalServices but not creating new lists. This means as soon as you modify this reference from another place in your code, it will be reflected in the GlobalServices list as well. All you have to do is:
public void setAssignedList(List<Leads> assignedList) {
this.assignedList = new ArrayList<>(assignedList);
}
public void setUnAssignedList(List<Leads> unAssignedList) {
this.unAssignedList = new ArrayList<>(unAssignedList);
}
public void setListInventory(List<Inventory> listInventory) {
this.listInventory = new ArrayList<>(listInventory);
}
This way a new copy will be created in memory for each list and the data will be overwritten.

Sorry if I was wrong, but your code here is not a problem.
The problem might come from other part of your application.
The data you set might be the data that extend your current data.
Example you have
GlobalServices instance = GlobalServices.getInstance()
List<Inventory> listInventory1 = new ArrayList<>();
listInventory1.add(new Inventory());
instance.setListInventory(listInventory1); // now your inventory have one item
// In some where else in your project
List<Inventory> listInventory2 = instance.getListInventory(); // lisInventorys.size() equals 1
// Then you add more data to listInventory2 by mistake
listInventory2.add(new Inventory()); // listInventory2.size() equals 2
// Then you set back listInventory2 to your global service
instance.setListInventory(listInventory2); // now your inventory have two item
So, the data had been actually overwrite, it data just been extended by accident.

Access arraylist from another class

I am a newbie to Java and I have a gui class which has a GUI component and it takes the input from the text field and should pass it to another class. The action listener of the button is below.
public void actionPerformed(ActionEvent action) {
arraylist.add(textField_1.getText());
arraylist.add(textField_2.getText());
arraylist.add(textField_3.getText());
arraylist.add(textField_4.getText());
}
since it is a void method I cannot return the array list so that Ii cannot construct a getter.
public ArrayList<String> getList(){
return this.arraylist;
}
Could anyone please tell me how to access this arraylist from the another class without passing it through the constructor? I am sorry if i asked anything wrong. Thanks in advance.

This is one of the many possible approaches.
Just define another class and call the setter from your actionPerformed(..) method.
public class YourOtherClass {
private static ArrayList<String> arraylist;
public void setList(arrayList) {
this.arraylist = arraylist;
}
public ArrayList<String> getList() {
return this.arraylist;
}
}
Now you can simply set this arraylist as:
public void actionPerformed(ActionEvent action) {
arraylist.add(textField_1.getText());
arraylist.add(textField_2.getText());
arraylist.add(textField_3.getText());
arraylist.add(textField_4.getText());
YourOtherClass.setList(arraylist);
}
Now when you want to access the contents of this list, simply use:
...
//any other method
ArrayList<String> arraylist = YourOtherClass.getList();
System.out.println(arraylist.get(0)); //or whatever
...

You can make that arraylist as Static and access it.
To access that particular arraylist use the below syntax
classNameThatContainArraylist.yourArrayList
be careful while using static.

If you want to use to set and get data then there are many approaches and two of them are follow
public class SetDataInArrayList {
//Aproach one by using object
private List<ActionEvent> list;
public SetDataInArrayList() {
list = new ArrayList();
}
public void setDataInList(ActionEvent e) {
list.add(e);
}
public List<ActionEvent> getList() {
return list;
}
//Approach two by using static reference
private static List<ActionEvent> newList;
static {
newList = new ArrayList<>();
}
public static void add(ActionEvent e) {
newList.add(e);
}
public static List<ActionEvent> returnList() {
return newList;
}
if you use either of approach you will need reference variable in both of cases to fetch data

If I understood, you want to do it:
public class A {
private ArrayList<String> arrayList;
public ArrayList<String> getArrayList() {
return this.arrayList;
}
}
public class B {
private A a = new A();
public void actionPerformed(ActionEvent action) {
a.getArrayList().add(textField_1.getText());
a.getArrayList().add(textField_2.getText());
a.getArrayList().add(textField_3.getText());
a.getArrayList().add(textField_4.getText());
}
}

GWT Editors - how to add N sub-editors of the same type based on a Collection

I have an object, Supply, that can either be an ElecSupply or GasSupply (see related question).
Regardless of which subclass is being edited, they all have a list of BillingPeriods.
I now need to instantiate N number of BillingPeriodEditors based on the contents of that list, and am pretty baffled as to how I should do it.
I am using GWTP. Here is the code of the SupplyEditor I have just got working:
public class SupplyEditor extends Composite implements ValueAwareEditor<Supply>
{
private static SupplyEditorUiBinder uiBinder = GWT.create(SupplyEditorUiBinder.class);
interface SupplyEditorUiBinder extends UiBinder<Widget, SupplyEditor>
{
}
#Ignore
final ElecSupplyEditor elecSupplyEditor = new ElecSupplyEditor();
#Path("")
final AbstractSubTypeEditor<Supply, ElecSupply, ElecSupplyEditor> elecSupplyEditorWrapper = new AbstractSubTypeEditor<Supply, ElecSupply, ElecSupplyEditor>(
elecSupplyEditor)
{
#Override
public void setValue(final Supply value)
{
setValue(value, value instanceof ElecSupply);
if(!(value instanceof ElecSupply))
{
showGasFields();
}
else
{
showElecFields();
}
}
};
#Ignore
final GasSupplyEditor gasSupplyEditor = new GasSupplyEditor();
#Path("")
final AbstractSubTypeEditor<Supply, GasSupply, GasSupplyEditor> gasSupplyEditorWrapper = new AbstractSubTypeEditor<Supply, GasSupply, GasSupplyEditor>(
gasSupplyEditor)
{
#Override
public void setValue(final Supply value)
{
setValue(value, value instanceof GasSupply);
if(!(value instanceof GasSupply))
{
showElecFields();
}
else
{
showGasFields();
}
}
};
#UiField
Panel elecPanel, gasPanel, unitSection;
public SupplyEditor()
{
initWidget(uiBinder.createAndBindUi(this));
gasPanel.add(gasSupplyEditor);
elecPanel.add(elecSupplyEditor);
}
// functions to show and hide depending on which type...
#Override
public void setValue(Supply value)
{
if(value instanceof ElecSupply)
{
showElecFields();
}
else if(value instanceof GasSupply)
{
showGasFields();
}
else
{
showNeither();
}
}
}
Now, as the list of BillingPeriods is a part of any Supply, I presume the logic for this should be in the SupplyEditor.
I got some really good help on the thread How to access PresenterWidget fields when added dynamically, but that was before I had implemented the Editor Framework at all, so I think the logic is in the wrong places.
Any help greatly appreciated. I can post more code (Presenter and View) but I didn't want to make it too hard to read and all they do is get the Supply from the datastore and call edit() on the View.
I have had a look at some examples of ListEditor but I don't really get it!

You need a ListEditor
It depends of how you want to present them in your actual view, but the same idea apply:
public class BillingPeriodListEditor implements isEditor<ListEditor<BillingPeriod,BillingPeriodEditor>>, HasRequestContext{
private class BillingPeriodEditorSource extends EditorSource<BillingPeriodEditor>{
#Override
public EmailsItemEditor create(final int index) {
// called each time u add or retrive new object on the list
// of the #ManyToOne or #ManyToMany
}
#Override
public void dispose(EmailsItemEditor subEditor) {
// called each time you remove the object from the list
}
#Override
public void setIndex(EmailsItemEditor editor, int index) {
// i would suggest track the index of the subeditor.
}
}
private ListEditor<BillingPeriod, BillingPeriodEditor> listEditor = ListEditor.of(new BillingPeriodEditorSource ());
// on add new one ...
// apply or request factory
// you must implement the HasRequestContext to
// call the create.(Proxy.class)
public void createNewBillingPeriod(){
// create a new one then add to the list
listEditor.getList().add(...)
}
}
public class BillingPeriodEditor implements Editor<BillingPeriod>{
// edit you BillingPeriod object
}
Then in you actual editor edit as is in the path Example getBillingPeriods();
BillingPeriodListEditor billingPeriods = new BillingPeriodListEditor ();
// latter on the clickhandler
billingPeriods.createNewBillingPeriod()
You are done now.

Java: Filling a JComboBox with objects

I'm trying to fill a jComboBox with objects. I have it working in one class, but in this class it's giving a NullPointerException but the code is almost the same. What am I missing here?
The code I'm using to fill the comboboxes:
I have translated every variable to English and removed some unnescessary stuff. I hope it's more clear for you guys now:
package unive.billing.boundary.clientmanager.frames;
import unive.billing.control.ClientsManager;
import unive.billing.control.InsuranceManager;
/**
*
* #author Forza
*/
public class ClientFrame extends javax.swing.JFrame {
/**
* Creates new form AddClientGUI
*/
private ClientsManager clientmanager;
private InsuranceManager insurancemanager;
public ClientFrame() {
initComponents();
clientmanager = new ClientsManager();
clientmanager.printList();
updateComboBoxCompany();
updateComboBoxInsurance();
}
private ClientsManager clientmanager;
private InsuranceManager insurancemanager;
public ClientFrame() {
initComponents();
clientmanager = new ClientsManager();
clientmanager.printList();
updateComboBoxCompany();
updateComboBoxInsurance();
}
public void updateComboBoxCompany()
{
for (Object object : insurancemanager.getCompanyNames())
{
companyComboBox.addItem(object);
}
}
public void updateComboBoxInsurance()
{
for (Object object : insurancemanager.getPolicyNames())
{
insuranceComboBox.addItem(object);
}
}
Here are the methods used:
public Object[] getCompanyNames()
{
ArrayList<String> cnames = new ArrayList<String>();
for (InsurancesCompany company : insurancecompanyList)
{
cnames.add(company.getCompanyName());
}
return cnames.toArray();
}
public Object[] getPolicyNames()
{
ArrayList<String> vnames = new ArrayList<String>();
for (Insurance insurance : insuranceList)
{
vnames.add(insurance.getPolicyName());
}
return vnames.toArray();
}
This is how my lists are initialized:
public class InsuranceManager {
private String insurancePath;
private String insurancecompanyenPath;
private static List<InsurancesCompany> insurancecompanyList;
private static List<Insurance> insuranceList;
private Insurance currentInsurance;
public InsuranceManager() {
insurancecompanyenPath = "Files/company.txt";
insurancePath = "Files/insurance.txt";
insuranceList = new List<>();
}
public void createNewList()
{
insurancecompanyList = new List<>();
System.out.println("Creates list");
}
public Object[] getCompanyNames()
{
ArrayList<String> cnames = new ArrayList<String>();
for (InsurancesCompany company : insurancecompanyList)
{
cnames.add(company.getCompanyName());
}
return cnames.toArray();
}
public Object[] getPolicyNames()
{
ArrayList<String> vnames = new ArrayList<String>();
for (Insurance insurance : insuranceList)
{
vnames.add(insurance.getPolicyName());
}
return vnames.toArray();
}
Edit: Here's the MainGUI which calls createNewList (maakLijstAan)
private ClientsManager clientsmanager;
private BillingManager billingmanager;
private InsuranceManager insurancemanager;
public MainGUI() {
clientsmanager = new ClientsManager();
clientsmanager.CreateNewList();
insurancemanager = new InsuranceManager();
insurancemanager.CreateNewList();
insurancemanager.loadInsuranceCompanyList();
initComponents();
jMenuItem1.setText("Save clients");
jMenuItem2.setText("Load clients");
jMenuItem3.setText("Exit");
}

You never initialize verzekeringBeheer, therefore you get a NullPointerException when you try to invoke methods on that variable.
You should have somewhere in your constructor, something like this:
verzekeringbeheer = new VerzekeringBeheer();
Also, try to avoid making your code coupled with other parts of your code. For example:
public VerzekeringBeheer() {
...
//verzekeringmaatschappijLijst is never initialized!!!
}
public void maakLijstAan()
{
verzekeringmaatschappijLijst = new Lijst<>();
System.out.println("Maak lijst aan");
}
public Object[] getMaatschappijNamen()
{
ArrayList<String> mnamen = new ArrayList<String>();
// Here you use verzekeringmaatschappijLijst without checking that is not null!!!
for (VerzekeringsMaatschappij maatschappij : verzekeringmaatschappijLijst)
{
mnamen.add(maatschappij.getMaatschappijNaam());
}
return mnamen.toArray();
}
If nobody calls maakLijstAan, you will get a NullPointerException in getMaatschappijNamen. Try to avoid code that is so dependent of external code, in order to run without problems.

all data for JComboBox are stored in ComboBoxModel
set ComboBoxModel for proper Objects type (String, Integer, Icon or simple Object), Java7 implements Generics, there are significant differiences in compare with Java6
all updates (to the JComboBox or its Model) must be done on Event Dispatch Thread

I only see you useing variables but for me they are nit initialized. So they are null and you get a NPE.
So how are verzekeringmaatschappijLijst and verzekeringLijst initialized?

How to get reference to an anonymous object 2 levels up

I have code like this:
TextBox txt = new TextBox(){
public void onLoad(){
this.addFocusHandler(new FocusHandler(){
//some codes here
//if I use "this" keyword, it refers to the handler, but how can I get a reference to the textbox?
});
}
};
Question is embedded in the position.
Edit:
In respect to the answers, the creation of a pre-defined reference works for this situation, but this apparently lost (or at least reduce) the benefits of anonymous object/function.
I hope to find a way without creating a new reference. Rather just to get the reference from that scope.
After all the answers, here is a conclusion:
Reflection does not work in GWT. (at least I did not succeed) obj.getClass() works, but others like getMethods() or getEnclosingClass() don't work.
The way to get a reference can either be declaring a reference in the right scope, or get a higher level object reference and reference downwards. I prefer the latter simply because you don't need to create a new variable.

TextBox txt = new TextBox(){
public void onLoad(){
final TextBox finalThis = this;
this.addFocusHandler(new FocusHandler(){
finalThis.doSomething();
);
}
};

The enclosing instance of a non-static inner class (anonymous or named) in Java is available as ClassName.this, i.e.
TextBox txt = new TextBox(){
public void onLoad(){
this.addFocusHandler(new FocusHandler(){
doSomethingCleverWith(TextBox.this);
});
}
};

This has worked for me in the past. It works in client side js too. Here is a reference to more detail
What is the difference between Class.this and this in Java
public class FOO {
TextBox txt = new TextBox(){
public void onLoad(){
this.addFocusHandler(new FocusHandler(){
#Override
public void onFocus(FocusEvent event) {
FOO.this.txt.setHeight("100px");
}
});
}
};
}

This may work for you:
TextBox txt = new TextBox(){
public void onLoad(){
final TextBox ref = this;
this.addFocusHandler(new FocusHandler(){
public void doSomething(){
//some codes
ref.execute();
}
});
}
};
But I prefer to migrate inner classes to named classes:
public class Test {
public void demo(){
TextBox txt = new TextBox(){
public void onLoad(){
this.addFocusHandler(new DemoFocusHandler(this));
}
};
}
}
External FocusHandler:
public class DemoFocusHandler extends FocusHandler {
private TextBox textBox;
public DemoFocusHandler(TextBox textBox){
this.textBox = textBox;
}
public void doSomething(){
//some codes
textBox.execute();
}
}

If gwt supported reflection you could do something along the lines of this:
final TextBox txt = new TextBox() {
public void onLoad() {
final Object finalThis = this;
this.addFocusHandler(new FocusHandler() {
#Override
public void onFocus(FocusEvent event) {
try {
Method method= finalThis.getClass().getMethod("getVisibleLength");
method.invoke(finalThis);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
};
Without reflection the existing answers are you best bet. There are two gwt reflection projects gwt reflection and gwt-preprocessor both are in beta and I have not tried them.