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over reliance on one arrayList

public class InventorySetDAO{
public LinkedList<CustomInventory> inventories = new LinkedList<>();
}
I am developing plugin that add/delete data in arraylist. and There's too much reference on the arrayList from other class.
Class InventoryItemModifier:
public class InventoryItemModifier {
InventorySetDAO inventorySetDAO;
public InventoryItemModifier(InventorySetDAO inventorySetDAO){
this.inventorySetDAO = inventorySetDAO;
}
public void addItem(ItemStack itemStack, ClickAction click, RequiredItems requiredItems) {
Bukkit.getPluginManager().callEvent(new ItemAddedEvent());
inventorySetDAO.getLastInventory().addItem(itemStack, click, requiredItems);
}
public void removeItem(ItemStack itemStack){
Bukkit.getPluginManager().callEvent(new ItemRemovedEvent());
inventorySetDAO.getLastInventory().removeItem(itemStack);
}
}
Class InventoryPlayerAccessor:
public class InventoryPlayerAccessor {
InventorySetDAO inventorySetDAO;
public boolean openPage(Player player) {
if (!inventories.isEmpty()) {
inventories.get(0).openInventory(player);
return true;
}
return false;
}
public boolean openPage(Player player, int index) {
if (!inventories.isEmpty()) {
if (index >= 0 && index < inventories.size()) {
inventories.get(index).openInventory(player);
return true;
}
}
return false;
}
}
I think there is risk of manipualte arrayList unproperly, so I think arrayList must be in a class and provide methods(add/insert/remove...) but if then there are too much responsibilities in that class.
I tried to seperate them into multiple classes, but it doesn't seem to solve this problem. is there a way to reduce reliance on arrayList, or efficient way to encapsulate arrayList?

To reduce each classes reliance on the underlying ArrayList (or just List), you could think about using the composite pattern instead of the DAO pattern. This would hide all/most of the logic to the InventorySet class.
class InventorySet {
private final List<CustomInventory> inventories = new ArrayList<>();
public void addItem() { }
public void removeItem() { }
}
Then, you can just keep your InventoryPlayerAccessor (maybe rename) but compose it of a InventorySet for easy access.
class InventorySetView {
void open();
}

Calling a method originated from a switch case from another class

I am relatively new to java and I have been assigned a project. I need to make a rather complicated(for a newbie) battleship game.
Here, I try to call switch cases in class Player from class Tile. Since I've read that one can't directly have access to a switch case, I have made the methods caseSea(), caseShip() e.t.c.
When trying to call them in class Player I get a 'void' type not allowed here error, which I understand but have no idea how to fix!
Any help would be appreciated thanks!
Here is class Tile created to represent one block of a 2D array that will become the battleground board:
public class Tile
{
private int x,y;
static boolean hidden;
public Action tile_action;
public enum Action
{
Sea,
Ship,
Hit,
Miss
}
Action action;
public Tile(Action action)
{
this.action=action;
this.x = x;
this.y = y;
this.tile_action = action;
}
public static void caseSea()
{
System.out.println("~");
}
public static void caseShip()
{
if(hidden == true)
System.out.println("~");
else
System.out.println("s");
}
public static void caseHit()
{
System.out.println("X");
}
public static void caseMiss()
{
System.out.println("O");
}
public static void draw(Action action)
{
switch(action)
{
case Sea:
caseSea();
break;
case Ship:
caseShip();
break;
case Hit:
caseHit();
break;
case Miss:
caseMiss();
break;
}
}
}
Also here is class Player which contains the call to the switch case:
import java.util.Scanner;
public class Player
{
String username; //Variable declaration
static int shotcount;
static int misscount;
static int hitcount;
static int repeatshot;
private int HitPosition[][] = new int[10][10];
public Player(String username)
{
this.username = username;
}
private void placeAllShips()
{
//super.placeAllShips();
}
public void fire(int pos[],int board,boolean hit)
{
if(hit == true)
{
HitPosition[pos[0]][pos[1]] = Tile.draw(Tile.caseHit());
shotcount++;
hitcount++;
}
else
{
HitPosition[pos[0]][pos[1]] = Tile.draw(Tile.caseMiss());
shotcount++;
misscount++;
}
}
}
I get the error that I mention above, in Tile.draw(Tile.caseHit()) and Tile.draw(Tile.caseMiss())

Heh, since this is a relatively simple issue I wanted to stick to comments, but I feel I need to make my voice since the other answers are simply wrong.
What the other guys are suggesting is changing the return type of the methods, and that indeed can work but not with the code you have.
They would ultimately be called twice, and thats not what you want.
The call order would be
caseHit()
pass the caseHit()'s value to draw()
enter a switch inside the draw() method with the Hit enum value and ultimately call caseHit() again.
This is not what you want to do. All you wanna do is call the draw() method with the right argument, which in this case is one of the Action enum values.
So ultimately there is a very easy way to fix your code without much changes and this is changing
Tile.draw(Tile.caseHit());
to
Tile.draw(Tile.Action.Hit);
(and by analogy the other calls of this method)

With Tile.draw(Tile.caseHit()) you are trying to call the caseHit() method and sending the return value of that method as a parameter to the draw() method. The problem is that the caseHit() method isn't returning anything as it has a void return type.
You could fix this by making the caseHit() method return an Action:
public static Action caseHit() {
return Action.Hit;
}

How to add a hook to save event for existing DataObject in NetBeans?

I want to make some processing every time when a particular DataObject is saved. If I understand NetBeans IDE API correctly, there is an Savable interface that can be used to implement saving options for custom editors. The problem here is that I do not want to implement my own editor, nor DataObject. I have a MIME type that is edited by a default Gsf editor (the common scripting language api) and has a GsfDataObject (I expect with the DOSavable). I want to keep all that way, just to add a hook, maybe a callback method or something, that would be called every time a save is done upon a given GsfDataObject (and I want a default save action be called, I dont want to override it).
So far I came to this simple solution but it seems ugly (it is more or less inspired by http://wiki.netbeans.org/DevFaqListenForSaveEvents ):
// I have a FileObject fobj
final DataObject dobj = DataObject.find(fobj);
dobj.addPropertyChangeListener(new PropertyChangeListener() {
#Override
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getPropertyName().equals(DataObject.PROP_MODIFIED)) {
if (!((Boolean) evt.getOldValue()) & ((Boolean) evt.getNewValue())) {
System.out.println(">>>> here it gets modified");
} else {
System.out.println(">>>> here the data object gets saved");
}
}
}
});
However, this is not called only when the save is done, but also when the file gets modified, but then the modifications are reverted by Ctrl + Z. It only checks whether the data object changes its state from modified to unmodified. Is there a way to hook to a save event only?
P.S.: I tried to call new SJDOSavable(dobj).add(); in the moment when the DataObject gets modified and then to remove it in the other branch. However, the handleSave method does not get called. SJDOSavable class is a simple Savable implemented according to DOSavable from the DataSystems API:
private static final class SJDOSavable extends AbstractSavable implements Icon {
final DataObject obj;
public SJDOSavable(DataObject obj) {
this.obj = obj;
}
#Override
public String findDisplayName() {
return obj.getNodeDelegate().getDisplayName();
}
#Override
protected void handleSave() throws IOException {
System.out.println(">>>>> but this does not get called");
}
#Override
public boolean equals(Object other) {
if (other instanceof SJDOSavable) {
SJDOSavable dos = (SJDOSavable) other;
return obj.equals(dos.obj);
}
return false;
}
#Override
public int hashCode() {
return obj.hashCode();
}
final void remove() {
unregister();
}
final void add() {
register();
}
#Override
public void paintIcon(Component c, Graphics g, int x, int y) {
icon().paintIcon(c, g, x, y);
}
#Override
public int getIconWidth() {
return icon().getIconWidth();
}
#Override
public int getIconHeight() {
return icon().getIconHeight();
}
private Icon icon() {
return ImageUtilities.image2Icon(obj.getNodeDelegate().getIcon(BeanInfo.ICON_COLOR_16x16));
}
}

Did you try this ?
http://wiki.netbeans.org/DevFaqListenForSaveEvents
Also if you want to listen to global Save events, it seems you can do that now.
https://netbeans.org/bugzilla/show_bug.cgi?id=140719

method does not override or implement a method from a supertype error

I'm trying to design an undo/redo mechanism to my Chess game.. I decided to use stack data structure which is going to build on an ArrayList.. I also want that my UndoStack and RedoStack classes should be singleton.. However i'm getting
method does not override or implement a method from a supertype
pop() in UndoStack cannot implement pop() in IStackable
return type Move is not compatible with cgas5.Move
where Move is a type-variable:
Move extends Object declared in class UndoStack
error..
Here is my IStackable interface:
package cgas5;
public interface IStackable {
abstract public Move pop();
abstract public void push(Move m);
}
and my UndoStack class
package cgas5;
import java.util.ArrayList;
public class UndoStack<Move> extends ArrayList<Move> implements IStackable {
UndoStack undoStack;
private UndoStack() {
undoStack = new UndoStack();
}
public UndoStack getUndoStack() {
if (undoStack == null) {
undoStack = new UndoStack();
}
return undoStack;
}
#Override
public Move pop() {
Move m = get(size() - 1);
remove(size() - 1);
return m;
}
#Override
public void push(Move m) {
add(m);
}
}
and if it's necessary my Move class:
package cgas5;
public class Move {
private Piece pieceToMove;
private Square currentSquare;
private Square targetSquare;
private Piece capturedPiece;
private Piece promotedPiece;
public Move(){
}
public Move(Piece pieceToMove, Square currentSquare, Square targetSquare){
this.pieceToMove = pieceToMove;
this.currentSquare = currentSquare;
this.targetSquare = targetSquare;
}
public Piece getPieceToMove() {
return pieceToMove;
}
public void setPieceToMove(Piece pieceToMove) {
this.pieceToMove = pieceToMove;
}
public Square getCurrentSquare() {
return currentSquare;
}
public void setCurrentSquare(Square currentSquare) {
this.currentSquare = currentSquare;
}
public Square getTargetSquare() {
return targetSquare;
}
public void setTargetSquare(Square targetSquare) {
this.targetSquare = targetSquare;
}
public Piece getCapturedPiece() {
return capturedPiece;
}
public void setCapturedPiece(Piece capturedPiece) {
this.capturedPiece = capturedPiece;
}
public Piece getPromotedPiece() {
return promotedPiece;
}
public void setPromotedPiece(Piece promotedPiece) {
this.promotedPiece = promotedPiece;
}
}
Thanks in advance..

This is the problem:
public class UndoStack<Move> extends ArrayList<Move>
That's using Move as a generic type parameter, whereas really you don't want a generic type at all - you just want to use Move as the type argument for ArrayList<E>. You want:
public class UndoStack extends ArrayList<Move>
That should fix the problem - although personally I'd strongly recommend using composition instead of inheritance here. (In other words, make your UndoStack type contain an ArrayList<Move> - or something similar - rather than subclassing it.)
Additionally, this is never going to work:
UndoStack undoStack;
private UndoStack() {
undoStack = new UndoStack();
}
That means that to create an UndoStack, you need to create another UndoStack... how do you expect that to happen? You'll currently get a stack overflow exception... why do you need the variable at all?

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.