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Is there any way to delete entries of an arraylist dynamically

As you can see from the image below I want to select something from my table ( which changes whenever I press a button from the vertical box to the left i.e "Overview", "Orders" ... ) and delete the record from an array ( i.e. where the content comes from ).
The method I approached bellow works but it is not elegant since I have to create at most 8 if statements for each button id. Is there any way to delete the content dynamically. Is there any way for the JVM to figure out which record belongs to which array list?
TableController
#FXML
private TableView<Object> defaultTableView;
public void delete(){
if( MockServer.getServer().currentButton.equals("btnIngredients"))
MockServer.getServer().removeIngredient(defaultTableView.getSelectionModel().getSelectedItem());
else if ( MockServer.------.equals("btnOrders"))
MockServer.getServer().removeOrder(defaultTableView.getSelectionModel().getSelectedItem());
}
Controller
#FXML
private TableController tableController;
#FXML
public void deleteRecord(ActionEvent event){
tableController.delete();
}
MockServer
public class MockServer implements ServerInterface {
public Restaurant restaurant;
public ArrayList<Dish> dishes = new ArrayList<Dish>();
public ArrayList<Drone> drones = new ArrayList<Drone>();
public ArrayList<Ingredient> ingredients = new ArrayList<Ingredient>();
public ArrayList<Order> orders = new ArrayList<Order>();
public ArrayList<Staff> staff = new ArrayList<Staff>();
public MockServer(){}
public ArrayList<Ingredient> getIngredients() { return this.ingredients; }
public ArrayList<Order> getOrders() { return this.orders; }
public ArrayList<Staff> getStaff() { return this.staff; }
....
static public ServerInterface getServer(){
return server;
}
#Override
public void removeIngredient(Ingredient ingredient) {
int index = this.ingredients.indexOf(ingredient);
this.ingredients.remove(index);
this.notifyUpdate();
}
}

This pseudocode will need refactoring since I don't have all the code that you are using but I wish that you will get the general idea
Ok I believe that in the button click code you have to tell your mock server which list is currently used try adding this to the mock server
List currentList = null;
public void setCurrentList(String listName) { // you can use integer but the best is to use enum type setCurrentList(enum) this way you will get tapeSafety
switch(listName){
case "ingredients" : currentList = ingredients ; break;
//other cases
default : throw new Exception(" list not referred error with key value"+listName);
}
}
public void delete(Object o){
int index = this.currentList.indexOf(o);
this.currentList.remove(index);
}
now you can update you controller delete as bellow
public void delete(){
MockServer.getServer().delete(defaultTableView.getSelectionModel().getSelectedItem());
}
Why this should work?
you have to know that there is a good practice that says code to an interface, not an implementation
As you know List in java is an interface so when I assigned the ingredients object this interface will reference the same ArrayList as the object and it will take all it behaviours (how to search for an ingredient object etc...) this way when we will use the currentList on runtime after a button click we are sure that the currentList will be the same as the clicked list and pointing to the same list in the memory
Wish this simple and really resume explanation could help you

How to make a List<Entity> on a variable with a cast

so I am trying to make a Minecraft plugin that listens to the configuration file for input of which mobs to not target players. Here is what I have so far
public class ZombieListener implements Listener {
private final List<String> entities;
public ZombieListener(List<String> entities){
this.entities = entities;
}
#EventHandler
public void onEntityTargetEvent(EntityTargetLivingEntityEvent event) {
if (event.getTarget() event.getTarget() instanceof Player ) {
final Player targeted = (Player) event.getTarget();
if (targeted.hasPermission("dont.target.me") && entities.contains(targeted)){
event.setCancelled(true);
}
}
}
}
I realise that I can't check for an entity from an object and therefore I need to make targeted a List. How should I do this?

The other answer is way more complex than it needs to be. Try to do this instead:
public class ZombieListener implements Listener {
private final List<String> entities;
public ZombieListener(List<String> entities){
this.entities = entities;
}
#EventHandler
public void onEntityTargetEvent(EntityTargetLivingEntityEvent event) {
if (event.getTarget() instanceof Player && entities.contains(event.getEntityType().getName())) {
final Player targeted = (Player) event.getTarget();
if (targeted.hasPermission("dont.target.me") && entities.contains(targeted)) {
event.setCancelled(true);
}
}
}
}
All I did was add a small bit of code in the first if-statement:
entities.contains(event.getEntityType().getName())
This makes it so the application checks if the entity is one of the affected types, and carries on with the listener accordingly.
Hope this helps!

Use the entity class instead.
For example I created a mod that caused animals to age over time, making them die (they also would breed on their own). In order to allow the config to determine how quickly animals aged, I used the animal class:
private Class species;
private Entity entity;
public EntityAIAging(Random random, EntityAnimal ent, Class spec, EntityAgeTracker ageTracker) {
species = spec;
entity = ent;
//...
}
public void updateTask() {
// Both of these function the same:
// Unaging animals do not age, do not die, and do not procreate
if(HardLibAPI.animalManager.isUnaging(species)) {
return;
}
if(HardLibAPI.animalManager.isUnaging(entity.getClass())) {
return;
}
//...
}
So what you'd want to do is call entity.getClass() and check if it exists within a List<Class> entities. If you want to see how I parsed a config file to locate classes, you can see that code here. Its complicated and has some additional logic to handle minor misspellings.

java add object to arrayList

I read most of the other things on SO and I couldn't seem to find an answer.
Don't know how to write an add method. I'm getting a StackOverflowError. It seems to run infinitely which I am not sure why.
Also, just wanted to confirm that it is possible to write a print function that prints out everything in arraylist myPolygon right?
class IrregularPolygon{
private ArrayList <Point2D.Double> myPolygon;
// constructors
public IrregularPolygon() { }
// public methods
public void add(Point2D.Double aPoint) {
//System.out.println("in");
this.add(aPoint);
System.out.println("finished");
// for (Point2D.Double number : myPolygon) {
// System.out.println("Number = " + aPoint);
// }
}
}
public class App{
public static void main(String[] args){
IrregularPolygon polygon = new IrregularPolygon();
Point2D.Double point = new Point2D.Double(1.2, 2.3);
System.out.println(point);
polygon.add(point);
} // main
} // class

Calling this.add(aPoint) in add is a recursive call. This method calls itself, and there is no base case, so this results in a StackOverflowError once it recurses deeply enough.
It looks like you want to add it to the ArrayList, so change
this.add(aPoint);
to
myPolygon.add(aPoint);
In addition, you never initialized myPolygon, so it's null. Initialize it:
private ArrayList <Point2D.Double> myPolygon = new ArrayList<>();

Values getting modified in the class during the runtime

I am trying to loop around the value that already got populated in Registration class. I have already put a breakpoint in getInstance() method in Registration class. When the cursor reaches the below for loop code.
for (final Registration.HolderEntry entry : Registration.getInstance()) {
// do other things..
}
I do a F5 on that. And then it gooes to getInstance() method of Registration class (below is the class). And when I inspect on instance variable at that point, I always see values populated in listOfBundles list which is good.
But if I keep on pressing F5 again, at some point it comes to iterator method in Registration class and then if I inspect on listOfBundles list, I don't see any values in that list which is what I am not able to understand why it is happening like this. No other code is running which might change the value of listOfBundles.
public class Registration implements Iterable<Registration.HolderEntry> {
private List<String> listOfBundles = new LinkedList<String>();
private final Map<String, HolderEntry> bundleMapper = new HashMap<String, HolderEntry>();
private Registration() {
//
}
private static class BundlesHolder {
static final Registration instance = new Registration();
}
public static Registration getInstance() {
return BundlesHolder.instance;
}
public synchronized void registerBundles(final String bundleName, final IBundleCollection collection) {
HolderEntry bundleHolder = new HolderEntry(bundleName, collection);
bundleMapper.put(bundleName, bundleHolder);
listOfBundles.add(bundleName);
}
#Override
public synchronized Iterator<HolderEntry> iterator() {
List<String> lst = new LinkedList<String>(listOfBundles);
List<HolderEntry> list = new LinkedList<HolderEntry>();
for (String clName : lst) {
if (bundleMapper.containsKey(clName)) {
list.add(bundleMapper.get(clName));
}
}
Collections.reverse(list);
return list.iterator();
}
// some other code
}
I hope the question is clear enough. Can anybody tell me what wrong I am going here?

because you use static instance always return same object from
public static Registration getInstance()
method. (only one time Registration is initialize).
there are no different object is your iteration. same object is iterating on your iteration. its not like applying to every object changes you make while iterate but it is same object you iterate and change values.
I dont know your real requirement. but try to use this.
public static Registration getInstance() {
return new Registration();;
}

Accessing private access variable data from different class

I have this Thread inside my Project which runs continously accepting new symbols
public class StreamThread extends Thread {
private Set<String> allSymbolSet = new HashSet<String>(Arrays.asList("USBC", "TCSD", "PCLJ"));
private PriorityBlockingQueue<String> priorityBlocking = new PriorityBlockingQueue<String>();
public void addSymbols(String str) {
if (str != null) {
priorityBlocking.add(str);
}
}
public void run() {
while (true) {
try {
while (priorityBlocking.peek() != null) {
String symbol = priorityBlocking.poll();
allSymbolSet.add(symbol);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
my question is , i want to access the variable allSymbolSet from another class
what will be the best approach to get access to this variable named allSymbolSet from anoter class , for this i have two choices
modify the access specifier of allSymbolSet from private to default .
Write a get Method which is supoused to return the Set
Please suggest me , what will be the good approach in this case ??

Best approach would be the getter method AND synchronize the access to the object allSymbolSet, something like this:
public Set<String> getAllSymbolSet() {
synchronized(allSymbolSet) {
return allSymbolSet;
}
}
and also synchronize the access to allSymbolSet inside your thread.

A few comments:
If you make the set non-private, some code could modify it (by mistake or on purpose) which could result in inconsistent behaviour in your StreamThread class. Don't do that.
Providing a simple getter does not solve the issue above. Prefer returning a copy of your set.
Make your variables final whenever you can when in a multi-threading environment - it solves many thread safety issues.
Prefer implementing Runnable than extending Thread
You will need to synchronize ALL accesses to your set (read and write), for example by using a synchronizedSet or even better by wrapping a ConcurrentHashMap which generally provides better performance.
instead of peek+poll you can simply take from your queue
So your final class could look like:
public class StreamTask implements Runnable {
private final Set<String> allSymbolSet;
private final PriorityBlockingQueue<String> priorityBlocking = new PriorityBlockingQueue<String>();
public StreamTask() {
String[] symbols = {"USBC", "TCSD", "PCLJ"};
//use a thread safe set, for example based on ConcurrentHashMap
allSymbolSet = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean> ());
Collections.addAll(allSymbolSet, symbols);
}
public void addSymbols(String str) {
if (str != null) {
priorityBlocking.add(str);
}
}
public Set<String> getSymbols() {
return new HashSet<> (allSymbolSet); //return a copy
}
public void run() {
while (true) {
try {
allSymbolSet.add(priorityBlocking.take());
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
Finally, I might be missing something, but that class looks equivalent to the much simpler:
public class StreamTask {
private final Set<String> allSymbolSet;
public StreamTask() {
String[] symbols = {"USBC", "TCSD", "PCLJ"};
//use a thread safe set, for example based on ConcurrentHashMap
allSymbolSet = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean> ());
Collections.addAll(allSymbolSet, symbols);
}
public void addSymbols(String str) {
if (str != null) {
allSymbolSet.add(str);
}
}
public Set<String> getSymbols() {
return new HashSet<> (allSymbolSet); //return a copy
}
}

Better way is method 2. Writing a getter method. If you want to allow set the values then use a setter later. Then your data will be encapsulated .

Write a get Method which is supposed to return the Set. by using this your private remains private and you also access it from outside using Object of the same class.